845 lines
31 KiB
Scheme
845 lines
31 KiB
Scheme
;;; Rebirth Lisp implemented in Birth Lisp (self-hosting)
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||
;;;
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;;; Copyright (C) 2017 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 GIBBLE LISP ITSELF 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---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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;;; 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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;; Here we define the libprebirth primitives. When we first compile Rebirth
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;; with Birth, `string->es' is not yet available, because it is only
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;; implemented in Rebirth. Further, Birth includes libprebirth in its
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;; output, so we cannot blindly redefine the procedures without producing an
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;; error.
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;;
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;; Once Rebirth is compiled with Birth, Rebirth can then compile
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;; itself. Since Rebirth _does_ implement `string->es', and further _does not_
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;; include libprebirth in its output, we can define the libprebirth
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;; primitives ourselves in Rebirth Lisp. Cut the cord.
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;;
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;; Some of these definitions aren't valid: variable arguments, for example,
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;; aren't represented _at all_---the `define' form will be properly
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;; implemented in the future to correct this.
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(cond-expand
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(string->es
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(define #t (string->es "true"))
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(define #f (string->es "false"))
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;; _truep is used only internally and is still defined as a JS function
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;; for brevity
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(string->es "const _truep = x => x !== false")
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(define (es:typeof x)
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(string->es "typeof $$x"))
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(define (symbol=? x y)
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(and (string=? (es:typeof x) "symbol")
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(eq? x y)))
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(define (es:arg->arr args)
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(string->es "Array.prototype.slice.call($$args)"))
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(define (list)
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(es:arg->arr (string->es "arguments")))
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;; warning: only compares two values
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(define (= x y)
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(string->es "+$$x === +$$y"))
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(define (> x y)
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(string->es "+$$y > +$$x"))
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(define (< x y)
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(string->es "+$$y < +$$x"))
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;; warning: doesn't verify that it's a pair
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(define (length xs)
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(string->es "$$xs.length"))
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(define (es:array? xs)
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(string->es "Array.isArray($$xs)"))
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(define (es:-assert-list xs)
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(or (es:array? xs)
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(error "expecting list")))
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(define (es:-assert-pair xs)
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(es:-assert-list xs)
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(if (= 0 (length xs))
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(error "expecting pair")
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#t))
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;; ignore obj for now
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(define (error msg obj)
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(string->es "throw Error($$msg)")
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#f) ; prevent above from being in tail position and prefixing "return"
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;; warning: these only operate on arrays
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(define (cons obj1 obj2)
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(es:-assert-list obj2)
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(string->es "[$$obj1].concat($$obj2)"))
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(define (car pair)
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(es:-assert-pair pair)
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(string->es "$$pair[0]"))
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(define (cdr pair)
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(es:-assert-pair pair)
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(string->es "$$pair.slice(1)"))
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(define (append)
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(fold (lambda (x xs)
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(es:-assert-list x)
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(string->es "$$xs.concat($$x)"))
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(list)
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(es:arg->arr (string->es "arguments"))))
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;; warning: these two are wholly inadequate
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(define (list? xs)
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(string->es "Array.isArray($$xs)"))
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(define (pair? xs)
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(and (list? xs)
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(> 0 (length xs))))
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;; R7RS string
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(define (substring s start end)
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(string->es "$$s.substring($$start, $$end)"))
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(define (string-length s)
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(string->es "$$s.length"))
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(define (string=? s1 s2)
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(string->es "typeof $$s1 === 'string' && $$s1 === $$s2"))
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(define (string-ref s i)
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(string->es "$$s[$$i] || $$error(`value out of range: ${$$i}`)"))
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(define (string-append)
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(let ((args (es:arg->arr (string->es "arguments"))))
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(string->es "$$args.join('')")))
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(define (eq? x y)
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(string->es "$$x === $$y"))
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;; R7RS math
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(define (+)
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(let ((args (es:arg->arr (string->es "arguments"))))
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(fold (lambda (y x)
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(string->es "$$x + $$y"))
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0
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args)))
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(define (-)
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(let ((args (es:arg->arr (string->es "arguments"))))
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(fold (lambda (y x)
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(string->es "$$x - $$y"))
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(car args)
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(cdr args))))
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(define (zero? x)
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(eq? x 0))
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;; SRFI-1
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;; warning: fold here only supports one list
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(define (fold f init xs)
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(string->es "$$xs.reduce((prev, x) => $$f(x, prev), $$init)"))
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;; warning: map here uses the length of the first list, not the shortest
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;; (we implement this in ES for now so that we don't have to augment
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;; Prebirth Lisp to support the "rest" procedure definition syntax)
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(define (map f)
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(string->es "__a = arguments") ; because let introduces a function
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(let* ((args (es:arg->arr (string->es "__a")))
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(xs (cdr args)))
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(string->es
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"$$xs[0].map((_, i) => $$f.apply(null, $$xs.map(x => x[i])))")))
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(define (js:regexp s opts)
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(string->es "new RegExp($$s, $$opts)"))
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(define (js:match r s)
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(string->es "$$s.match($$r) || false"))
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(define (js:replace r repl s)
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(string->es "$$s.replace($$r, $$repl)"))
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(define *fsdata*
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(if (string->es "typeof __fsinit === 'undefined'")
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(string->es "{}")
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(string->es "__fsinit")))
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(define *fs*
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(if (string->es "typeof require === 'undefined'")
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(string->es
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"{
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readFileSync(path)
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{
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throw Error(`Cannot load ${path} (no fs module)`);
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},
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}")
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(string->es "require('fs')")))
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;; so that we do not have to modify existing compiler output (which would
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;; break the first round of compilation before these are defined)
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(string->es "const fsdata = $$$k$fsdata$k$")
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(string->es "const fs = $$$k$fs$k$")
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(define (js:file->string path)
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(if (string->es "fsdata[$$path] === undefined")
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(string->es
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"fsdata[$$path] = fs.readFileSync($$path).toString()")
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(string->es "fsdata[$$path]")))))
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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 (js:match-regexp re s)
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(js:match (js: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 `js:while' and `js: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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(js:while #t ; browser stack workaround
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(let* ((ws (or (js: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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(js: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 (js: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 (js: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 (js: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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||
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||
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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.
|
||
;; 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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||
|
||
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||
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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.
|
||
(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
|
||
(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
|
||
;; 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))))
|
||
|
||
|
||
;; 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))
|
||
|
||
|
||
|
||
;; Produce an AST from the given string SRC of sexps
|
||
;;
|
||
;; This is essentially the CST with whitespace removed. It first invokes
|
||
;; the lexer to produce a token string from the input sexps SRC. From this,
|
||
;; it verifies only proper nesting (that SRC does not close sexps too early
|
||
;; and that EOF isn't reached before all sexps are closed) and produces an
|
||
;; AST that is an isomorphism of the original sexps.
|
||
(define (parse-lisp src)
|
||
;; accessor methods to make you and me less consfused
|
||
(define (ast-depth ast) (car ast))
|
||
(define (ast-tree ast) (cadr ast))
|
||
(define (ast-stack ast) (caddr ast))
|
||
|
||
|
||
;; perform a leftmost reduction on the token string
|
||
(define (toks->ast toks)
|
||
(fold
|
||
(lambda (token result)
|
||
(let ((depth (ast-depth result))
|
||
(xs (ast-tree result))
|
||
(stack (ast-stack result))
|
||
(type (token-type token))
|
||
(pos (token-pos token)))
|
||
|
||
;; there are very few token types to deal with (again, this is a
|
||
;; very simple bootstrap lisp)
|
||
(case type
|
||
;; ignore comments
|
||
(("comment") result)
|
||
|
||
;; when beginning a new expression, place the expression
|
||
;; currently being processed onto a stack, allocate a new list,
|
||
;; and we'll continue processing into that new list
|
||
(("open") (list (+ depth 1)
|
||
(list)
|
||
(cons xs stack)))
|
||
|
||
;; once we reach the end of the expression, pop the parent off of
|
||
;; the stack and append the new list to it
|
||
(("close") (if (zero? depth)
|
||
(parse-error src pos
|
||
"unexpected closing parenthesis")
|
||
(list (- depth 1)
|
||
(append (car stack) (list xs))
|
||
(cdr stack))))
|
||
|
||
;; strings and symbols (we cheat and just consider everything,
|
||
;; including numbers and such, to be symbols) are just copied
|
||
;; in place
|
||
(("string" "symbol") (list depth
|
||
(append xs (list token))
|
||
stack))
|
||
|
||
;; we should never encounter anything else unless there's a bug
|
||
;; in the tokenizer or we forget a token type above
|
||
(else (parse-error
|
||
src pos (string-append
|
||
"unexpected token `" type "'"))))))
|
||
(list 0 (list) (list)) ; initial 0 depth; empty tree; expr stack
|
||
toks))
|
||
|
||
|
||
;; lex the input SRC and pass it to `toks->ast' to generate the AST;
|
||
;; if the depth is non-zero after we're done, then we're unbalanced.
|
||
(let* ((toks (lex src 0))
|
||
(ast (toks->ast toks)))
|
||
(if (zero? (ast-depth ast))
|
||
(ast-tree ast)
|
||
;; if we terminate at a non-zero depth, that means there ar still
|
||
;; open sexps
|
||
(error (string-append
|
||
"unexpected end of input at depth "
|
||
(ast-depth ast))))))
|
||
|
||
|
||
;; Generate ECMAScript-friendly name from the given id.
|
||
;;
|
||
;; A subset of special characters that are acceptable in Scheme are
|
||
;; converted in an identifiable manner; others are simply converted to `$'
|
||
;; in a catch-all and therefore could result in conflicts and cannot be
|
||
;; reliably distinguished from one-another. Remember: this is temporary
|
||
;; code.
|
||
(define (tname->id name)
|
||
(if (js:match (js:regexp "^\\d+$") name)
|
||
name
|
||
(string-append
|
||
"$$" (js:replace (js:regexp "[^a-zA-Z0-9_]" "g")
|
||
(lambda (c)
|
||
(case c
|
||
(("-") "$_$")
|
||
(("?") "$7$")
|
||
(("@") "$a$")
|
||
(("!") "$b$")
|
||
((">") "$g$")
|
||
(("#") "$h$")
|
||
(("*") "$k$")
|
||
(("<") "$l$")
|
||
(("&") "$n$")
|
||
(("%") "$o$")
|
||
(("+") "$p$")
|
||
(("=") "$q$")
|
||
(("^") "$v$")
|
||
(("/") "$w$")
|
||
(("$") "$$")
|
||
(else "$")))
|
||
name))))
|
||
|
||
;; Join a list of strings XS on a delimiter DELIM
|
||
(define (join delim xs)
|
||
(if (pair? xs)
|
||
(fold (lambda (x str)
|
||
(string-append str delim x))
|
||
(car xs)
|
||
(cdr xs))
|
||
""))
|
||
|
||
|
||
;; Compile parameter list.
|
||
;;
|
||
;; This simply takes the value of the symbol and outputs it (formatted),
|
||
;; delimited by commas.
|
||
(define (params->es params)
|
||
(join ", " (map (lambda (t)
|
||
(tname->id (token-value t)))
|
||
params)))
|
||
|
||
|
||
;; Compile body s-expressions into ECMAScript
|
||
;;
|
||
;; This produces a 1:1 mapping of body XS s-expressions to ES statements,
|
||
;; recursively. The heavy lifting is done by `sexp->es'.
|
||
(define (body->es xs ret)
|
||
;; recursively process body XS until we're out of pairs
|
||
(if (not (pair? xs))
|
||
""
|
||
(let* ((x (car xs))
|
||
(rest (cdr xs))
|
||
(more? (or (not ret) (pair? rest))))
|
||
;; the result is a semicolon-delimited string of statements, with
|
||
;; the final statement prefixed with `return' unless (not ret)
|
||
(string-append
|
||
" "
|
||
(if more? "" "return ") ; prefix with `return' if last body exp
|
||
(sexp->es x) ";" ; process current body expression
|
||
(if (pair? rest) "\n" "")
|
||
(body->es rest ret))))) ; recurse
|
||
|
||
|
||
;; Compile variable or procedure definition into ES
|
||
;;
|
||
;; This performs a crude check to determine whether a procedure definition
|
||
;; was supplied: if the cadr of the given token T is itself token, then it
|
||
;; is considered to be a variable.
|
||
(define (cdfn t)
|
||
(if (token? (cadr t))
|
||
(cdfn-var t) ;; (define foo ...)
|
||
(cdfn-proc t))) ;; (define (foo ...) ...)
|
||
|
||
|
||
;; Compile variable definition into ES
|
||
;;
|
||
;; This compiles the token T into a simple let-assignment.
|
||
(define (cdfn-var t)
|
||
(let* ((dfn (cadr t))
|
||
(id (tname->id (token-value dfn)))
|
||
(value (sexp->es (caddr t))))
|
||
(string-append "let " id "=" value)))
|
||
|
||
|
||
;; Compile procedure definition into an ES function definition
|
||
;;
|
||
;; This will fail if the given token is not a `define'.
|
||
(define (cdfn-proc t)
|
||
;; e.g. (define (foo ...) body)
|
||
(let* ((dfn (cadr t))
|
||
(id (tname->id (token-value (car dfn))))
|
||
(params (params->es (cdr dfn)))
|
||
(body (body->es (cddr t) #t)))
|
||
;; this is the final format---each procedure becomes its own function
|
||
;; definition in ES
|
||
(string-append
|
||
"function " id "(" params ")\n{\n" body "\n};")))
|
||
|
||
|
||
;; Quote an expression
|
||
;;
|
||
;; If SEXP is a token, produce an ECMAScript Symbol. Otherwise,
|
||
;; recursively apply to each element in the list.
|
||
;;
|
||
;; TODO: This implementation isn't wholly correct---numbers, for example,
|
||
;; 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 (string=? type "unquote-splicing"))))
|
||
(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)
|
||
(("unquote-splicing")
|
||
(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) "])")))
|
||
|
||
|
||
;; Function/procedure aliases and special forms
|
||
;;
|
||
;; And here we have what is probably the most grotesque part of this file.
|
||
;;
|
||
;; This map allows for a steady transition---items can be removed as they
|
||
;; are written in Prebirth Lisp. This should give us a sane (but still
|
||
;; simple) environment with which we can start to self-host.
|
||
;;
|
||
;; 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 ARS is the list of arguments.
|
||
;;
|
||
;; These are by no means meant to be solid implementations; notable
|
||
;; deficiencies are documented, but don't expect this to work properly in
|
||
;; every case. They will be replaced with proper R7RS implementations in
|
||
;; the future (Rebirth).
|
||
(define (fnmap fn args t)
|
||
(case fn
|
||
(("js:console")
|
||
(string-append "console.log(" (map sexp->es args) ")"))
|
||
(("js:error")
|
||
(string-append "console.error(" (map sexp->es args) ")"))
|
||
|
||
;; very primitive cond-expand
|
||
(("cond-expand")
|
||
(let* ((clause (car args))
|
||
(feature (token-value (car clause)))
|
||
(body (cdr clause)))
|
||
(case feature
|
||
(("string->es") (body->es body #f))
|
||
(else ""))))
|
||
|
||
;; output raw code into the compiled ECMAScript (what could go wrong?)
|
||
(("string->es")
|
||
(token-value (car args)))
|
||
|
||
;; yes, there are more important things to do until we get to the
|
||
;; point where it's worth implementing proper tail calls
|
||
(("js: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)")))
|
||
(("js:break") "__whilebrk=true")
|
||
|
||
;; note that the unquote forms are only valid within a quasiquote; see
|
||
;; that procedure for the handling of those forms
|
||
(("quote") (quote-sexp (car args)))
|
||
(("quasiquote") (quasiquote-sexp (car args)))
|
||
|
||
(("define") (cdfn t))
|
||
|
||
(("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) ";}"
|
||
(if (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)
|
||
(let ((var (car binding))
|
||
(init (cadr binding)))
|
||
(string-append " let " (sexp->es var)
|
||
" = " (sexp->es init) ";\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))))
|
||
|
||
;; normal procedure application
|
||
(else (let* ((idfn (tname->id fn))
|
||
(argstr (join ", " (map sexp->es args))))
|
||
(string-append idfn "(" argstr ")")))))
|
||
|
||
|
||
;; 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") (tname->id (token-value 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)
|
||
;; compiled output, wrapped in a self-executing function to limit scope
|
||
;; (note that we no longer depend on libprebirth)
|
||
(string-append "(function(){"
|
||
(join "\n\n" (map sexp->es ast))
|
||
"})();"))
|
||
|
||
|
||
;; at this point, this program can parse itself and output a CST (sans
|
||
;; whitespace)
|
||
(js:console (rebirth->ecmascript
|
||
(parse-lisp
|
||
(js:file->string "/dev/stdin"))))
|