859 lines
33 KiB
Scheme
859 lines
33 KiB
Scheme
;;; Rebirth Lisp implemented in Birth and Rebirth Lisp (self-hosting)
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;;;
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;;; Copyright (C) 2017, 2018 Mike Gerwitz
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;;;
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;;; This file is part of Gibble.
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;;;
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;;; Gibble is free software: you can redistribute it and/or modify
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;;; it under the terms of the GNU Affero General Public License as
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;;; published by the Free Software Foundation, either version 3 of the
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;;; License, or (at your option) any later version.
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;;;
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;;; This program is distributed in the hope that it will be useful,
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;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU Affero General Public License
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;;; along with this program. If not, see <http://www.gnu.org/licenses/>.
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;;;
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;;; THIS IS TEMPORARY CODE that will be REWRITTEN IN ULAMBDA SCHEME after
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;;; a very basic bootstrap is complete. It is retained as an important
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;;; artifact for those who wish to build Gibble from scratch without using
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;;; another version of Gibble itself. This is called "self-hosting".
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;;;
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;;; This is the compiler for Rebirth Lisp---it builds off of Birth by
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;;; first eliminating the need for libprebirth; this allows _all_
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;;; development to happen in a Lisp dialect, which liberates the last
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;;; remaining process that isn't technically self-hosted. So, Rebirth
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;;; completes the raw, self-hosting bootstrapping process.
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;;;
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;;; To continue with the creepy birthing puns, you can consider libprebirth
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;; to be the umbilical cord. After Birth, it's still attached---here we
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;;; cut it.
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;;;
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;;; Of course, bootstrapping can't end there: we need a fully functioning
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;;; Scheme compiler. Rebirth may as well be called Rerebirth, or
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;;; Rererebirth, or Re*birth, or Reⁿbirth---it is a recursively self-hosting
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;;; compiler. It adds features to itself each time it compiles itself.
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;;;
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;;; The ultimate goal after all of those compilation steps is to produce a
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;;; compiler that can support the actual Scheme to be used by Gibble:
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;;; Ulambda Scheme (abbreviated "Y Scheme", for an upside-down lambda, where
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;;; "Y" stands for the Y combinator). More on the name in the future
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;;; (perhaps see the Ulambda documentation).
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;;;
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;;; Note that we're dealing with a small subset of Scheme here, so certain
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;;; things might be done differently given a proper implementation.
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;;;
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;;; This is an exact copy of `birth.scm', modified to introduce additional
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;;; features. This is important, since Birth is a 1:1 translation of the
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;;; Prebirth compiler and needs to stay that way. This fork allows us to
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;;; vary as much as we want from the initial implementation. See the commit
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;;; history for this file for more information as to how it evolved (the
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;;; first commit is the direct copy before actual code changes).
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;;;
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;;; This file follows a narrative (from Birth to Reⁿbirth), but it's more of
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;;; a choose-your-adventure-book-style narrative: order of certain
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;;; definitions unfortunately matters in this simple implementation. For
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;;; example, primitive macros (e.g. `if') must be defined before they are
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;;; used, so those appear at the top of this file, despite their definitions
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;;; not being supported until future passes.
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;;;
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;;; So, to begin, goto STEP 0! ----------------,
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;;; V
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(cond-expand
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(include
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(include "rebirth/es.scm") ;; STEP 2 (start at STEP 0) <--,
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(include "rebirth/relibprebirth.scm") ;; STEP 0 (start here) /
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(include "rebirth/macro.scm"))) ;; STEP 1 (then go to STEP 2) -`
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;; pair selection
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(define (cadr xs)
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(car (cdr xs)))
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(define (caadr xs)
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(car (car (cdr xs))))
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(define (caddr xs)
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(car (cdr (cdr xs))))
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(define (cadddr xs)
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(car (cdr (cdr (cdr xs)))))
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(define (caddddr xs)
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(car (cdr (cdr (cdr (cdr xs))))))
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(define (cddr xs)
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(cdr (cdr xs)))
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(define (not x)
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(if x #f #t))
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;; for convenience
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(define (es:match-regexp re s)
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(es:match (es:regexp re) s))
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;; Convert source input into a string of tokens.
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;;
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;; This is the lexer. Whitespace is ignored. The grammar consists of
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;; simple s-expressions.
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;;
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;; Tokens are produced with `make-token'. The source SRC will be
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;; left-truncated as input is processed. POS exists for producing metadata
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;; for error reporting---it has no impact on parsing.
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;;
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;; This implementation was originally recursive and immutable, but the stack
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;; was being exhausted, so it was refactored into an inferior
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;; implementation. Note the use of `es:while' and `es:break'---these are
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;; quick fixes to the problem of stack exhaustion in browsers (where we have
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;; no control over the stack limit); proper tail call support will come
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;; later when we have a decent architecture in place.
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;;
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;; The result is a list of tokens. See `token' for the format.
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(define (lex src pos)
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(let ((toks (list)))
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(es:while #t ; browser stack workaround
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(let* ((ws (or (es:match-regexp "^\\s+"
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src)
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(list "")))
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(ws-len (string-length (car ws)))
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(trim (substring src ws-len)) ; ignore whitespace, if any
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(newpos (+ pos ws-len))) ; adj pos to account for removed ws
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(if (string=? "" trim)
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(es:break) ; EOF and we're done
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;; normally we'd use `string-ref' here, but then we'd have to
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;; implement Scheme characters, so let's keep this simple and keep
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;; with strings
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(let* ((ch (substring trim 0 1))
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(t (case ch
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;; comments extend until the end of the line
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((";") (let ((eol (es:match-regexp "^(.*?)(\\n|$)" trim)))
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(make-token "comment" (cadr eol) trim newpos)))
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;; left and right parenthesis are handled in the same
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;; manner: they produce distinct tokens with
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;; single-character lexemes
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(("(") (make-token "open" ch trim newpos))
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((")") (make-token "close" ch trim newpos))
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;; strings are delimited by opening and closing ASCII
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;; double quotes, which can be escaped with a
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;; backslash
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(("\"") (let ((str (es:match-regexp
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"^\"(|(?:.|\\\n)*?[^\\\\])\""
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trim)))
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(or str (parse-error
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src pos
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"missing closing string delimiter"))
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;; a string token consists of the entire
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;; string including quotes as its lexeme,
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;; but its value will be the value of the
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;; string without quotes due to the `str'
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;; match group (see `token')
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(make-token "string" str trim newpos)))
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(else
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;; anything else is considered a symbol up until
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;; whitespace or any of the aforementioned
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;; delimiters
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(let ((symbol (es:match-regexp "^[^\\s()\"]+"
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trim)))
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(make-token "symbol" symbol trim newpos))))))
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;; yikes---see notes in docblock with regards to why
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;; we're using mutators here
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(set! toks (append toks (list (car t))))
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(set! src (cadr t))
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(set! pos (caddr t))))))
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toks))
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;; Throw an error with a window of surrounding source code.
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;;
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;; The "window" is simply ten characters to the left and right of the
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;; first character of the source input SRC that resulted in the error.
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;; It's a little more than useless.
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(define (parse-error src pos msg)
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(let ((window (substring src (- pos 10) (+ pos 10))))
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(error (string-append msg " (pos " pos "): " window)
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src)))
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;; Produce a token, left-truncate src, and update pos.
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;;
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;; Unlike the JS Prebirth implementation which uses a key/value object,
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;; we're just using a simple list.
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;;
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;; The expected arguments are: the token type TYPE, the match group or
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;; string MATCH, left-truncated source code SRC, and the position POS
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;; relative to the original source code.
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(define (make-token type match src pos)
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(let* ((parts (if (list? match) match (list match match)))
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(lexeme (car parts))
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;; the value is the first group of the match (indicating what we
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;; are actually interested in), and the lexeme is the full match,
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;; which might include, for example, string delimiters
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(value (or (and (pair? (cdr parts))
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(cadr parts))
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lexeme))
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(len (string-length lexeme)))
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;; produce token and recurse on `lex', left-truncating the source
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;; string to discard what we have already processed
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(list (list (quote token) type lexeme value pos)
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(substring src len)
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(+ pos len))))
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;; various accessor procedures for token lists (we're Prebirth Lisp here,
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;; so no record support or anything fancy!)
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(define (token? t) (and (pair? t) (symbol=? (quote token) (car t))))
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(define (token-type t) (cadr t))
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(define (token-lexeme t) (caddr t))
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(define (token-value t) (cadddr t))
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(define (token-pos t) (caddddr t))
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;; Produce an AST from the given string SRC of sexps
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;;
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;; This is essentially the CST with whitespace removed. It first invokes
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;; the lexer to produce a token string from the input sexps SRC. From this,
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;; it verifies only proper nesting (that SRC does not close sexps too early
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;; and that EOF isn't reached before all sexps are closed) and produces an
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;; AST that is an isomorphism of the original sexps.
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(define (parse-lisp src)
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;; accessor methods to make you and me less confused
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(define (ast-depth ast) (car ast))
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(define (ast-tree ast) (cadr ast))
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(define (ast-stack ast) (caddr ast))
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;; perform a leftmost reduction on the token string
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(define (toks->ast toks)
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(fold
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(lambda (token result)
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(let ((depth (ast-depth result))
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(xs (ast-tree result))
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(stack (ast-stack result))
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(type (token-type token))
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(pos (token-pos token)))
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;; there are very few token types to deal with (again, this is a
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;; very simple bootstrap lisp)
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(case type
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;; ignore comments
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(("comment") result)
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;; when beginning a new expression, place the expression
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;; currently being processed onto a stack, allocate a new list,
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;; and we'll continue processing into that new list
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(("open") (list (+ depth 1)
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(list)
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(cons xs stack)))
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;; once we reach the end of the expression, pop the parent off of
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;; the stack and append the new list to it
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(("close") (if (zero? depth)
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(parse-error src pos
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"unexpected closing parenthesis")
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(list (- depth 1)
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(append (car stack) (list xs))
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(cdr stack))))
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;; strings and symbols (we cheat and just consider everything,
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;; including numbers and such, to be symbols) are just copied
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;; in place
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(("string" "symbol") (list depth
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(append xs (list token))
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stack))
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;; we should never encounter anything else unless there's a bug
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;; in the tokenizer or we forget a token type above
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(else (parse-error
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src pos (string-append
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"unexpected token `" type "'"))))))
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(list 0 (list) (list)) ; initial 0 depth; empty tree; expr stack
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toks))
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;; lex the input SRC and pass it to `toks->ast' to generate the AST;
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;; if the depth is non-zero after we're done, then we're unbalanced.
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(let* ((toks (lex src 0))
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(ast (toks->ast toks)))
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(if (zero? (ast-depth ast))
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(ast-tree ast)
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;; if we terminate at a non-zero depth, that means there ar still
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;; open sexps
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(error (string-append
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"unexpected end of input at depth "
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(ast-depth ast))))))
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;; Generate ECMAScript-friendly parameter name for the given token T.
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;;
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;; The generated name will not have any environment references and is
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;; suitable only for the immediate scope.
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(define (tparam->es t)
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(tname->id (token-value t)))
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;; Predicate determining whether NAME should be output verbatim as an
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;; ECMAScript identifier.
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;;
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;; This only returns #t for numbers.
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(define (tname-verbatim? name)
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(es:match (es:regexp "^\\d+$") name))
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;; Generate ECMAScript to reference the variable associated with the token T
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;; in the current environment.
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;;
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;; The "current" environment is relative to whatever context into which the
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;; caller places this generated code---that is, the environment is
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;; resolved by the runtime environment.
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;;
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;; If macro support is not yet compiled in, then this returns the identifier
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;; name _without_ the environment, just as Birth.
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(define (env-ref t)
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(let ((name (if (token? t)
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(token-value t)
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t)))
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(if (tname-verbatim? name)
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name
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(cond-expand
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(cdfn-macro
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(string-append "_env." (tname->id name)))
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(else
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(tname->id name))))))
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;; Generate ECMAScript-friendly name from the given id.
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;;
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;; A subset of special characters that are acceptable in Scheme are
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;; converted in an identifiable manner; others are simply converted to `$'
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;; in a catch-all and therefore could result in conflicts and cannot be
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;; reliably distinguished from one-another. Remember: this is temporary
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;; code.
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(define (tname->id name)
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(if (tname-verbatim? name)
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name
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(string-append
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"$$" (es:replace (es:regexp "[^a-zA-Z0-9_]" "g")
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(lambda (c)
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(case c
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(("-") "$_$")
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(("?") "$7$")
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(("@") "$a$")
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(("!") "$b$")
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((">") "$g$")
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(("#") "$h$")
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(("*") "$k$")
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(("<") "$l$")
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(("&") "$n$")
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(("%") "$o$")
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(("+") "$p$")
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(("=") "$q$")
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(("^") "$v$")
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(("/") "$w$")
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(("$") "$$")
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(else "$")))
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name))))
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;; Join a list of strings XS on a delimiter DELIM
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(define (join delim xs)
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(if (pair? xs)
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(fold (lambda (x str)
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(string-append str delim x))
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(car xs)
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(cdr xs))
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""))
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;; Compile parameter list.
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;;
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;; This takes the value of the symbol and outputs it (formatted), delimited
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;; by commas.
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;;
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;; Since we do not support actual pairs (yet), the "." syntax that normally
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;; denotes the cdr is retained and presents itself here. The form "(arg1,
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;; arg2 . rest)" creates a list `rest' containing all remaining arguments
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;; after that point. Conveniently, ECMAScript Harmony supports this
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;; natively with the "..." syntax.
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(define (params->es params)
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(define (%param-conv params)
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(let* ((param (car params))
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(name (token-value param))
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(id (tname->id name))
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(rest (cdr params)))
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(if (string=? name ".")
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(list (string-append
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"..." (car (%param-conv rest))))
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(if (pair? rest)
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(cons id (%param-conv rest))
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(list id)))))
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(if (pair? params)
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(join "," (%param-conv params))
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""))
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;; Compile body s-expressions into ECMAScript
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;;
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;; This produces a 1:1 mapping of body XS s-expressions to ES statements,
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;; recursively. The heavy lifting is done by `sexp->es'.
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(define (body->es xs ret)
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;; recursively process body XS until we're out of pairs
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(if (not (pair? xs))
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""
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(let* ((x (car xs))
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(rest (cdr xs))
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(more? (or (not ret) (pair? rest))))
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;; the result is a semicolon-delimited string of statements, with
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;; the final statement prefixed with `return' unless (not ret)
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(string-append
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" "
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(if more? "" "return ") ; prefix with `return' if last body exp
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(sexp->es x) ";" ; process current body expression
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(if (pair? rest) "\n" "")
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(body->es rest ret))))) ; recurse
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;; Place parameters PARAMS into the current environment.
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;;
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;; This is ugly so that Rebirth can support multiple implementations at
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;; once---those with environment support and those without.
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(define (env-params params)
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(join "\n"
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(map (lambda (param)
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(if (string=? (token-value param) ".")
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"" ; next param is the cdr
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(string-append (env-ref param) " = "
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(tparam->es param) ";")))
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params)))
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;; Compile variable or procedure definition into ES
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;;
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;; This performs a crude check to determine whether a procedure definition
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;; was supplied: if the cadr of the given token T is itself token, then it
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;; is considered to be a variable.
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(define (cdfn t)
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(if (token? (cadr t))
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(cdfn-var t) ;; (define foo ...)
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(cdfn-proc t #f))) ;; (define (foo ...) ...)
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;; Compile variable definition into ES
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;;
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;; This compiles the token T into a simple let-assignment.
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(define (cdfn-var t)
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(let* ((dfn (cadr t))
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(id (tname->id (token-value dfn)))
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(value (sexp->es (caddr t))))
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(string-append "let " id "=" value ";_env." id " = " id)))
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;; Compile procedure definition into an ES function definition
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;;
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;; This will fail if the given token is not a `define'.
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(define (cdfn-proc t id-override)
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;; e.g. (define (foo ...) body)
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(let* ((dfn (cadr t))
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(id (or id-override
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(tname->id (token-value (car dfn)))))
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(params (cdr dfn))
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(fparams (params->es params))
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(fenv (env-params params))
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(body (body->es (cddr t) #t)))
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;; this is the final format---each procedure becomes its own function
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;; definition in ES
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(string-append
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"function " id "(" fparams ")\n{"
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"return (function(_env){\n" fenv "\n"
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body
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"\n})(Object.create(_env));}"
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(if (string=? id "") "" (string-append ";_env." id " = " id)))))
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;; Quote an expression
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;;
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;; If SEXP is a token, produce an ECMAScript Symbol. Otherwise,
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;; recursively apply to each element in the list.
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;;
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;; TODO: This implementation isn't wholly correct---numbers, for example,
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;; should not be converted to symbols, as they already are one.
|
||
(define (quote-sexp sexp)
|
||
(if (token? sexp)
|
||
(case (token-type sexp)
|
||
(("string") (sexp->es sexp))
|
||
(else
|
||
(string-append "Symbol.for('" (token-value sexp) "')")))
|
||
(string-append
|
||
"[" (join "," (map quote-sexp sexp)) "]")))
|
||
|
||
|
||
;; Quasiquote an expression
|
||
;;
|
||
;; A quasiquoted expression acts just like a quoted expression with one
|
||
;; notable exception---quoting can be escaped using special forms. For
|
||
;; example, each of these are equivalent:
|
||
;;
|
||
;; (quasiquote (a 1 2 (unquote (eq? 3 4))))
|
||
;; (list (quote a) 1 2 (eq? 3 4))
|
||
;; (quasiquote (a (unquote-splicing (list 1 2)) (unquote (eq? 3 4))))
|
||
;;
|
||
;; TODO/WARNING: Normally "(quasiquote a (unquote-splicing b))" would
|
||
;; produce "(a . b)" in a proper Lisp, but we do not yet support proper
|
||
;; pairs at the time that this procedure was written; all cdrs are assumed
|
||
;; to be lists. So do not do that---always splice lists.
|
||
(define (quasiquote-sexp sexp)
|
||
;; get type of token at car of pair, unless not a pair
|
||
(define (%sexp-maybe-type sexp)
|
||
(and (pair? sexp)
|
||
(token? (car sexp))
|
||
(token-value (car sexp))))
|
||
|
||
;; recursively process the sexp, handling various types of unquoting
|
||
(define (%quote-maybe sexp delim)
|
||
(if (pair? sexp)
|
||
(let* ((item (car sexp))
|
||
(rest (cdr sexp))
|
||
(type (%sexp-maybe-type item))
|
||
(add-delim (not (or (string=? type "unquote-splicing")
|
||
(string=? type "unquote@")))))
|
||
(string-append
|
||
(case type
|
||
;; escape quoting, nest within
|
||
(("unquote")
|
||
(string-append (if delim "," "")
|
||
(sexp->es (cadr item))))
|
||
|
||
;; escape quoting, splice list into parent expression
|
||
;; (lazy kluge warning), along with an alias for brevity
|
||
;; given that we lack the ",@" syntax right now
|
||
(("unquote-splicing" "unquote@")
|
||
(string-append
|
||
"]).concat(" (sexp->es (cadr item)) ").concat(["))
|
||
|
||
;; anything else, we're still quasiquoting recursively
|
||
(else (string-append (if delim "," "")
|
||
(quasiquote-sexp item))))
|
||
|
||
;; continue processing this list
|
||
(%quote-maybe rest add-delim)))
|
||
""))
|
||
|
||
;; tokens fall back to normal quoting
|
||
(if (token? sexp)
|
||
(quote-sexp sexp)
|
||
(string-append
|
||
"([" (%quote-maybe sexp #f) "])")))
|
||
|
||
|
||
;; Statically expand expressions based on implementation features
|
||
;;
|
||
;; Support for `cond-expand' allows Rebirth to introduce new features each
|
||
;; time that it is compiled. If matched, expressions will be evaluated as
|
||
;; if they were entered in place of the `cond-expand' itself; otherwise,
|
||
;; the entire `cond-expand' expression as a whole will be discarded.
|
||
;;
|
||
;; Birth will always discard `cond-expand' expressions unless they contain
|
||
;; an `else' clause, which permits us to compile on the first pass without
|
||
;; error.
|
||
(define (expand-cond-expand args)
|
||
(if (pair? args)
|
||
(let* ((clause (car args))
|
||
(feature (token-value (car clause)))
|
||
(body (cdr clause)))
|
||
;; now we get meta
|
||
(cond-expand
|
||
(string->es
|
||
(case feature
|
||
(("string->es" "include" "else") (body->es body #f))
|
||
(else (if (es:defined? feature)
|
||
(body->es body #f)
|
||
(expand-cond-expand (cdr args))))))
|
||
;; if we're not yet compiled with Rebirth, then string->es will
|
||
;; not yet be available---but it _will_ be in Rebirth, so
|
||
;; compile cond-expand such that it marks it as supported
|
||
(else
|
||
(case feature
|
||
;; these two are always supported in Rebirth Lisp
|
||
(("string->es" "include" "else") (body->es body #f))
|
||
;; keep recursing until we find something (this allows us to
|
||
;; short-circuit, most notably with "else")
|
||
(else
|
||
(expand-cond-expand (cdr args)))))))
|
||
""))
|
||
|
||
|
||
;; Determine whether the given name NAME represents a macro.
|
||
;;
|
||
;; If `string->es' is not yet supported, then this procedure always
|
||
;; yields `#f'. Otherwise, the compiler runtime `_env.macros' is consulted.
|
||
;;
|
||
;; See `cdfn-macro' for more information.
|
||
(define (macro? name)
|
||
(cond-expand
|
||
(string->es
|
||
(string->es "_env.macros[$$name] !== undefined"))
|
||
(else #f)))
|
||
|
||
|
||
;; Determine if FN is a procedure or macro and apply it accordingly with
|
||
;; arguments ARGS.
|
||
;;
|
||
;; These actions represent two separate environments: If a macro, then the
|
||
;; call needs to be executed immediately within the context of the compiler
|
||
;; runtime. Otherwise, procedure applications are simply compiled to be
|
||
;; produced with the rest of the compiler output and will be run at a later
|
||
;; time within the context of the compiled program.
|
||
(define (apply-proc-or-macro fn args)
|
||
(if (macro? fn)
|
||
(string->es "_env.macros[$$fn].apply(null,$$args)")
|
||
;; Procedures are produced as part of the compiler output.
|
||
(let ((argstr (join ", " (map sexp->es args))))
|
||
(string-append (env-ref fn) "(" argstr ")"))))
|
||
|
||
|
||
;; Primitive special forms.
|
||
;;
|
||
;; These are forms that cannot be re-written as macros because of
|
||
;; chicken-and-egg issues. Since the Rebirth compiler is temporary, we're
|
||
;; not going to worry about getting rid of the rest of these.
|
||
;;
|
||
;; String values are simple function aliases. Function values take over
|
||
;; the compilation of that function and allow for defining special forms
|
||
;; (in place of macro support). The first argument FN is the name of the
|
||
;; function/procedure/form, and ARGS is the list of arguments.
|
||
(define (fnmap fn args t)
|
||
(case fn
|
||
;; output raw code into the compiled ECMAScript (what could go wrong?)
|
||
(("string->es")
|
||
(token-value (car args)))
|
||
|
||
;; very primitive cond-expand
|
||
(("cond-expand") (expand-cond-expand args))
|
||
|
||
;; Note that the unquote forms are only valid within a quasiquote; see
|
||
;; that procedure for the handling of those forms. Since we do not
|
||
;; support the special prefix form, we also offer "`quote" as a
|
||
;; shorthand for quasiquote.
|
||
(("quote") (quote-sexp (car args)))
|
||
(("quasiquote" "`quote") (quasiquote-sexp (car args)))
|
||
|
||
(("define") (cdfn t))
|
||
(("define-macro") (cdfn-macro t)) ; not defined until string->es cond
|
||
|
||
;; Defining `include' is trivial right now since we're not doing any
|
||
;; sort of static analysis---we just need to start compilation of the
|
||
;; requested file and inline it right where we are. Note that this
|
||
;; doesn't enclose the file in `begin', so this isn't yet proper.
|
||
(("include") (rebirth->ecmascript
|
||
(parse-lisp
|
||
(es:file->string (token-value (car args))))))
|
||
|
||
;; If we have macro support (`cdfn-macro'), then assume that they exist
|
||
;; and try to use them; otherwise, continue to use built-in forms, which
|
||
;; have been moved into `fnmap-premacro').
|
||
(else
|
||
(cond-expand
|
||
(cdfn-macro (apply-proc-or-macro fn args))
|
||
(else (fnmap-premacro fn args t))))))
|
||
|
||
|
||
;; Special forms to be removed on future Rebirth pass in favor of macros
|
||
;;
|
||
;; See Step 2 above for the replacement macro definitions.
|
||
(cond-expand
|
||
(cdfn-macro) ; our cond-expand does not support `else'
|
||
(else
|
||
(define (fnmap-premacro fn args t)
|
||
(case fn
|
||
(("es:console")
|
||
(string-append "console.log(" (map sexp->es args) ")"))
|
||
(("es:error")
|
||
(string-append "console.error(" (map sexp->es args) ")"))
|
||
|
||
;; yes, there are more important things to do until we get to the
|
||
;; point where it's worth implementing proper tail calls
|
||
(("es:while")
|
||
(let ((pred (car args))
|
||
(body (cdr args)))
|
||
(string-append
|
||
"(function(__whilebrk){"
|
||
"while (" (sexp->es pred) "){\n"
|
||
(body->es body #f) " if (__whilebrk) break;\n"
|
||
"}\n"
|
||
"})(false)")))
|
||
(("es:break") "__whilebrk=true")
|
||
|
||
(("lambda")
|
||
(let ((fnargs (car args))
|
||
(body (cdr args)))
|
||
(string-append
|
||
"function(" (join ", " (map sexp->es fnargs)) "){\n"
|
||
(body->es body #t)
|
||
"}")))
|
||
|
||
;; simple if statement with optional else, wrapped in a self-executing
|
||
;; function to simplify code generation (e.g. returning an if)
|
||
(("if")
|
||
(let ((pred (car args))
|
||
(t (cadr args))
|
||
(f (and (pair? (cddr args))
|
||
(caddr args))))
|
||
(string-append
|
||
"(function(){"
|
||
"if (_truep(" (sexp->es pred) ")){return " (sexp->es t) ";}"
|
||
(or (and (pair? f)
|
||
(string-append "else{return " (sexp->es f) ";}"))
|
||
"")
|
||
"})()")))
|
||
|
||
;; and short-circuits, so we need to implement it as a special form
|
||
;; rather than an alias
|
||
(("and")
|
||
(string-append
|
||
"(function(__and){\n"
|
||
(join "" (map (lambda (expr)
|
||
(string-append
|
||
"__and = " (sexp->es expr) "; "
|
||
"if (!_truep(__and)) return false;\n"))
|
||
args))
|
||
"return __and;})()"))
|
||
|
||
;; or short-circuits, so we need to implement it as a special form
|
||
;; rather than an alias
|
||
(("or")
|
||
(string-append
|
||
"(function(__or){\n"
|
||
(join "" (map (lambda (expr)
|
||
(string-append
|
||
"__or = " (sexp->es expr) "; "
|
||
"if (_truep(__or)) return __or;\n"))
|
||
args))
|
||
"return false;})()"))
|
||
|
||
;; (let ((binding val) ...) ...body), compiled as a self-executing
|
||
;; function which allows us to easily represent the return value of
|
||
;; the entire expression while maintaining local scope.
|
||
(("let*")
|
||
(let ((bindings (car args))
|
||
(body (cdr args)))
|
||
(string-append
|
||
"(function(){\n"
|
||
(join "" (map (lambda (binding)
|
||
(string-append
|
||
" let " (sexp->es (car binding))
|
||
" = " (sexp->es (cadr binding)) ";\n"))
|
||
bindings))
|
||
(body->es body #t) "\n"
|
||
" })()")))
|
||
|
||
;; similar to the above, but variables cannot reference one-another
|
||
(("let")
|
||
(let* ((bindings (car args))
|
||
(body (cdr args))
|
||
(fparams (join ", " (map sexp->es
|
||
(map car bindings))))
|
||
(fargs (join ", " (map sexp->es
|
||
(map cadr bindings)))))
|
||
(string-append "(function(" fparams "){\n"
|
||
(body->es body #t) "\n"
|
||
"})(" fargs ")")))
|
||
|
||
;; and here I thought Prebirth Lisp would be simple...but having
|
||
;; `case' support really keeps things much more tidy, so here we are
|
||
;; (note that it doesn't support the arrow form, nor does it support
|
||
;; expressions as data)
|
||
(("case")
|
||
(let ((key (car args))
|
||
(clauses (cdr args)))
|
||
(string-append
|
||
"(function(){const _key=" (sexp->es key) ";\n"
|
||
"switch (_key){\n"
|
||
(join ""
|
||
(map (lambda (data exprs)
|
||
(string-append
|
||
(if (and (token? data)
|
||
(string=? "else" (token-lexeme data)))
|
||
"default:\n"
|
||
(join ""
|
||
(map (lambda (datum)
|
||
(string-append
|
||
"case " (sexp->es datum) ":\n"))
|
||
data)))
|
||
(body->es exprs #t) "\n"))
|
||
(map car clauses)
|
||
(map cdr clauses)))
|
||
"}})()")))
|
||
|
||
(("set!")
|
||
(let ((varid (car args))
|
||
(val (cadr args)))
|
||
(string-append (sexp->es varid) " = " (sexp->es val))))
|
||
|
||
;; procedure or macro
|
||
(else (apply-proc-or-macro fn args))))))
|
||
|
||
|
||
;; Convert s-expressions or scalar into ECMAScript
|
||
;;
|
||
;; T may be either an array of tokens or a primitive token (e.g. string,
|
||
;; symbol). This procedure is applied recursively to T as needed if T is
|
||
;; a list.
|
||
(define (sexp->es t)
|
||
(if (not (list? t))
|
||
(error "unexpected non-list for sexp->es token"))
|
||
|
||
(if (token? t)
|
||
(case (token-type t)
|
||
;; strings output as-is (note that we don't escape double quotes,
|
||
;; because the method of escaping them is the same in Scheme as it
|
||
;; is in ECMAScript---a backslash)
|
||
(("string") (string-append "\"" (token-value t) "\""))
|
||
|
||
;; symbols have the same concerns as procedure definitions: the
|
||
;; identifiers generated need to be ES-friendly
|
||
(("symbol") (env-ref t))
|
||
|
||
(else (error
|
||
(string-append
|
||
"cannot compile unknown token `" (token-type t) "'"))))
|
||
|
||
;; otherwise, process the expression
|
||
(fnmap (token-value (car t))
|
||
(cdr t)
|
||
t)))
|
||
|
||
|
||
;; Compile Rebirth Lisp AST into ECMAScript.
|
||
;;
|
||
;; The AST can be generated with `parse-lisp'.
|
||
(define (rebirth->ecmascript ast)
|
||
(join "\n\n" (map sexp->es ast)))
|
||
|
||
|
||
;; Compile Rebirth Lisp AST into an ECMAScript program.
|
||
;;
|
||
;; This compiles the AST into ECMAScript using `rebirth->ecmascript' and
|
||
;; then wraps it in a self-executing function to limit scope and create the
|
||
;; toplevel environment.
|
||
(define (rebirth->ecmascript-prog ast)
|
||
;; (note that we no longer depend on libprebirth)
|
||
(string-append "(function(_env){"
|
||
(rebirth->ecmascript ast)
|
||
"})({macros:{}});"))
|
||
|
||
|
||
;; at this point, this program can parse itself and output a CST (sans
|
||
;; whitespace)
|
||
(es:console (rebirth->ecmascript-prog
|
||
(parse-lisp
|
||
(es:file->string "/dev/stdin"))))
|