From 8ba1f04147d8f85e1a26fac2f91f91ecdad366d4 Mon Sep 17 00:00:00 2001
From: Mike Gerwitz <gerwitzm@lovullo.com>
Date: Mon, 24 Nov 2014 15:08:01 -0500
Subject: [PATCH] Partial application initial development

No support yet for recursive partial applications; just a basic concept.
---
 Makefile                       |   5 +-
 src/apply/partial.xsl          |  85 ++++++++++++++
 test/apply/partial-test.xsl    |  43 +++++++
 test/apply/partial.xspec       | 202 +++++++++++++++++++++++++++++++++
 test/transform/apply-gen.xspec |   4 +-
 5 files changed, 335 insertions(+), 4 deletions(-)
 create mode 100644 src/apply/partial.xsl
 create mode 100644 test/apply/partial-test.xsl
 create mode 100644 test/apply/partial.xspec

diff --git a/Makefile b/Makefile
index 4df9b82..ab7c49e 100644
--- a/Makefile
+++ b/Makefile
@@ -19,12 +19,13 @@
 path_src  := src
 path_test := test
 
-test_in_apply_gen := $(path_test)/transform/apply-gen-test-in.xsl.apply
+test_apply := $(path_test)/apply/partial-test.xsl.apply \
+              $(path_test)/transform/apply-gen-test-in.xsl.apply
 
 .PHONY: check test
 
 test: check
-check: $(test_in_apply_gen)
+check:  $(test_apply)
 	$(path_test)/runner
 
 %.apply: %
diff --git a/src/apply/partial.xsl b/src/apply/partial.xsl
new file mode 100644
index 0000000..14ad561
--- /dev/null
+++ b/src/apply/partial.xsl
@@ -0,0 +1,85 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Partial function application
+
+  Copyright (C) 2014 LoVullo Associates, Inc.
+
+    This file is part of hoxsl.
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+  Partial applications may only be used with dynamic functions
+  (functions compatible with `f:apply').
+-->
+
+<stylesheet version="2.0"
+  xmlns="http://www.w3.org/1999/XSL/Transform"
+  xmlns:xs="http://www.w3.org/2001/XMLSchema"
+  xmlns:f="http://www.lovullo.com/hoxsl/apply">
+
+
+<!--
+  Partially apply dynamic function reference FNREF
+
+  When provided to `f:apply', FNREF will be applied with ARGS as its
+  beginning argments, followed by any arguments to `f:apply'.
+
+  Note that you usually do not have to invoke this function directly:
+  the dynamic function calls will handle currying/partial application
+  for you, which has a much more inviting syntax.
+
+  TODO: Accept partial application as FNREF.
+-->
+<function name="f:partial">
+  <param name="fnref" as="element(f:ref)" />
+  <param name="args"  as="item()*" />
+
+  <f:ref>
+    <sequence select="$fnref/@*" />
+
+    <attribute name="partial"
+               select="count( $args )" />
+
+    <sequence select="$fnref/*" />
+  </f:ref>
+
+  <!-- nested sequences are implicitly flattened, so we're not
+       returning a sub-sequence here -->
+  <sequence select="$args" />
+</function>
+
+
+<!--
+  Determines whether FNREF is a partial application
+
+  You really should not rely on this for your code—it is intended for
+  internal use.  Instead, treat partial applications opaquely as their
+  own functions.
+-->
+<function name="f:is-partial" as="xs:boolean">
+  <param name="fnref" as="item()+" />
+
+  <!-- if we're passed a sequence, then the function portion of the
+       reference is first; all others are arguments -->
+  <variable name="fn"
+            select="$fnref[ 1 ]" />
+
+  <!-- we never want to fail, so we perform our type check here rather
+       than using param/@as -->
+  <sequence select="$fn instance of element(f:ref)
+                    and exists( $fn/@partial )
+                    and number( $fn/@partial ) gt 0" />
+</function>
+
+</stylesheet>
diff --git a/test/apply/partial-test.xsl b/test/apply/partial-test.xsl
new file mode 100644
index 0000000..0695395
--- /dev/null
+++ b/test/apply/partial-test.xsl
@@ -0,0 +1,43 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Tests partial function application
+
+  Copyright (C) 2014 LoVullo Associates, Inc.
+
+    This file is part of hoxsl.
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<stylesheet version="2.0"
+  xmlns="http://www.w3.org/1999/XSL/Transform"
+  xmlns:xs="http://www.w3.org/2001/XMLSchema"
+  xmlns:f="http://www.lovullo.com/hoxsl/apply"
+  xmlns:foo="http://www.lovullo.com/_junk">
+
+  <!-- SUT -->
+  <import href="../../src/apply/partial.xsl" />
+
+  <!-- generated -->
+  <import href="partial-test.xsl.apply" />
+
+
+  <function name="foo:ternary">
+    <param name="x" />
+    <param name="y" />
+    <param name="z" />
+
+    <sequence select="$x, $y, $z" />
+  </function>
+</stylesheet>
diff --git a/test/apply/partial.xspec b/test/apply/partial.xspec
new file mode 100644
index 0000000..8f0df53
--- /dev/null
+++ b/test/apply/partial.xspec
@@ -0,0 +1,202 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Tests partial function application
+
+  Copyright (C) 2014 LoVullo Associates, Inc.
+
+    This file is part of hoxsl.
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<description xmlns="http://www.jenitennison.com/xslt/xspec"
+             xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+             xmlns:x="http://www.jenitennison.com/xslt/xspec"
+             xmlns:f="http://www.lovullo.com/hoxsl/apply"
+             xmlns:foo="http://www.lovullo.com/_junk"
+             stylesheet="partial-test.xsl">
+
+  <scenario label="f:partial">
+    <variable name="fnref"
+              select="foo:ternary()" />
+
+    <variable name="args">
+      <foo:parent>
+        <foo:a />
+        <foo:b />
+        <foo:c />
+      </foo:parent>
+    </variable>
+
+
+    <scenario label="given an empty argument list">
+      <call function="f:partial">
+        <param name="fnref" select="$fnref" />
+        <param name="args"  select="()" />
+      </call>
+
+      <expect label="returns FNREF"
+              test="$x:result[ 1 ] = $fnref" />
+
+      <expect label="indicates that 0 arguments were partially applied"
+              test="$x:result/@partial = 0" />
+
+      <expect label="returns nothing else"
+              test="count( $x:result ) = 1" />
+    </scenario>
+
+
+    <scenario label="given arguments fewer than function param count">
+      <call function="f:partial">
+        <param name="fnref" select="$fnref" />
+        <param name="args"  select="$args/foo:a, $args/foo:b" />
+      </call>
+
+      <expect label="returns FNREF as first item in sequence"
+              test="$x:result[ 1 ] = $fnref" />
+
+      <expect label="indicates that N arguments were partially applied"
+              test="$x:result/@partial = 2" />
+
+      <expect label="returns each argument, ordered"
+              test="$x:result[ 2 ] = $args/foo:a
+                    and exists(
+                      $x:result[ 2 ]/parent::foo:parent )
+                    and $x:result[ 3 ] = $args/foo:b
+                    and exists(
+                      $x:result[ 3 ]/parent::foo:parent )" />
+    </scenario>
+
+
+    <scenario label="given arguments for all function params">
+      <call function="f:partial">
+        <param name="fnref" select="$fnref" />
+        <param name="args"  select="1, 2, 3" />
+      </call>
+
+      <expect label="returns FNREF as first item in sequence"
+              test="$x:result[ 1 ] = $fnref" />
+
+      <!-- we checked previously for argument values; we assume here
+           that it is working in this case...hopefully that is not
+           wrong! -->
+      <expect label="returns all arguments"
+              test="count( $x:result ) = 4" />
+    </scenario>
+  </scenario>
+
+
+  <scenario label="f:is-partial">
+    <scenario label="given a non-none">
+      <call function="f:is-partial">
+        <param name="fnref"
+               select="5" />
+      </call>
+
+      <expect label="returns false()"
+              test="$x:result = false()" />
+    </scenario>
+
+
+    <scenario label="given a non-fref node">
+      <call function="f:is-partial">
+        <param name="fnref">
+          <foo:moo />
+        </param>
+      </call>
+
+      <expect label="returns false()"
+              test="$x:result = false()" />
+    </scenario>
+
+
+    <!-- this leaks implementation details :x -->
+    <scenario label="given a non-fref node with spoofed attribute">
+      <call function="f:is-partial">
+        <param name="fnref">
+          <foo:moo partial="5" f:partial="5" />
+        </param>
+      </call>
+
+      <expect label="returns false()"
+              test="$x:result = false()" />
+    </scenario>
+
+
+    <scenario label="given a valid fref, not partially applied">
+      <call function="f:is-partial">
+        <param name="fnref"
+               select="foo:ternary()" />
+      </call>
+
+      <expect label="returns false()"
+              test="$x:result = false()" />
+    </scenario>
+
+
+    <!-- if partially applied with no arguments, then it may as well
+         not be; let's not alter the logic of callers just because it
+         was called with no effect -->
+    <scenario label="given a valid fref, partially applied with zero
+                     arguments">
+      <call function="f:is-partial">
+        <param name="fnref"
+               select="f:partial( foo:ternary(), () )" />
+      </call>
+
+      <expect label="returns false()"
+              test="$x:result = false()" />
+    </scenario>
+
+
+    <scenario label="given a valid fref, partially applied with N>0
+                     arguments, including argument sequence">
+      <call function="f:is-partial">
+        <param name="fnref"
+               select="f:partial( foo:ternary(), (1, 2) )" />
+      </call>
+
+      <expect label="returns true()"
+              test="$x:result = true()" />
+    </scenario>
+
+
+    <!-- caller may extract the function ref from the sequence and
+         assert on that -->
+    <scenario label="given a valid fref, partially applied with N>0
+                     arguments, without argument sequence">
+      <call function="f:is-partial">
+        <param name="fnref"
+               select="f:partial( foo:ternary(), (1, 2) )[ 1 ]" />
+      </call>
+
+      <expect label="returns true()"
+              test="$x:result = true()" />
+    </scenario>
+
+
+    <!-- we still want to consider all arguments to be a partial
+         application (consider it as producing a nullary
+         function)—otherwise, the abstraction is broken -->
+    <scenario label="given arguments for each parameter">
+      <call function="f:is-partial">
+        <param name="fnref"
+               select="f:partial( foo:ternary(), (1, 2, 3) )" />
+      </call>
+
+      <expect label="returns true()"
+              test="$x:result = true()" />
+    </scenario>
+  </scenario>
+</description>
diff --git a/test/transform/apply-gen.xspec b/test/transform/apply-gen.xspec
index df9dae9..51de570 100644
--- a/test/transform/apply-gen.xspec
+++ b/test/transform/apply-gen.xspec
@@ -73,7 +73,7 @@
           <xsl:function name="foo:bar">
             <xsl:param name="a" />
             <xsl:param name="b" as="xs:decimal" />
-            <xsl:param name="c" />"
+            <xsl:param name="c" />
           </xsl:function>
         </xsl:stylesheet>
       </context>
@@ -187,7 +187,7 @@
     <scenario label="f:arity">
       <call function="f:arity">
         <param name="fnref" select="foo:sub-two()" />
-      </call>"
+      </call>
 
       <expect label="is able to determine arity"
               test="$x:result = 2" />