From cd278c31d441acda3c4f91adec0b77d47ab97366 Mon Sep 17 00:00:00 2001
From: Mike Gerwitz <gerwitzm@lovullo.com>
Date: Sun, 30 Nov 2014 03:29:46 -0500
Subject: [PATCH] Partial applications now manipulate fnref arity

Previously, a separate `@partial' attribute was added to the ref and the
`@arity' maintained.  Unfortunately, this coupled `f:arity' with
`f:partial', which is unnecessary, considering that partial application is
supposed to conceptually yield a new function, which should be transparent
to `f:arity'.
---
 src/apply/partial.xsl    |  8 ++++----
 src/apply/ref.xsl        | 10 +++-------
 test/apply/partial.xspec | 33 ++++++++++++++++++---------------
 3 files changed, 25 insertions(+), 26 deletions(-)

diff --git a/src/apply/partial.xsl b/src/apply/partial.xsl
index 8a8fcba..98700be 100644
--- a/src/apply/partial.xsl
+++ b/src/apply/partial.xsl
@@ -98,8 +98,9 @@
       <f:ref>
         <sequence select="$ref/@*" />
 
-        <attribute name="partial"
-                   select="count( $argout )" />
+        <!-- the arity of the new partial application -->
+        <attribute name="arity"
+                   select="$arity - $argn" />
 
         <sequence select="$ref/*" />
       </f:ref>
@@ -128,8 +129,7 @@
   <!-- we never want to fail, so we perform our type check here rather
        than using param/@as -->
   <sequence select="$fn instance of element(f:ref)
-                    and exists( $fn/@partial )
-                    and number( $fn/@partial ) gt 0" />
+                    and exists( $fnref[ 2 ] )" />
 </function>
 
 
diff --git a/src/apply/ref.xsl b/src/apply/ref.xsl
index 8c6df09..3ea34de 100644
--- a/src/apply/ref.xsl
+++ b/src/apply/ref.xsl
@@ -135,16 +135,12 @@
   <variable name="ref" as="element( f:ref )"
             select="$fnref[ 1 ]" />
 
+  <!-- this implicitly asserts on the type; it should never fail if
+       the system is being used properly -->
   <variable name="arity" as="xs:integer"
             select="$ref/@arity" />
 
-  <variable name="partial" as="xs:integer"
-            select="if ( $ref/@partial ) then
-                      $ref/@partial
-                    else
-                      0" />
-
-  <sequence select="$arity - $partial" />
+  <sequence select="$arity" />
 </function>
 
 </stylesheet>
diff --git a/test/apply/partial.xspec b/test/apply/partial.xspec
index eda5a53..33e3743 100644
--- a/test/apply/partial.xspec
+++ b/test/apply/partial.xspec
@@ -51,11 +51,9 @@
         <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 reference to original target"
+              test="f:QName( $x:result[ 1 ] )
+                      = f:QName( $fnref )" />
 
       <expect label="returns nothing else"
               test="count( $x:result ) = 1" />
@@ -68,12 +66,13 @@
         <param name="args"  select="$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 target reference as first item in
+                     sequence"
+              test="f:QName( $fnref )
+                      = f:QName( $x:result[ 1 ] )" />
 
+      <!-- FIXME: this breaks the abstraction; use opaque
+           introspection -->
       <expect label="returns each argument, ordered"
               test="$x:result[ 2 ] is $args/foo:a
                     and $x:result[ 3 ] is $args/foo:b" />
@@ -108,8 +107,10 @@
         <param name="args"  select="$args/foo:b" />
       </call>
 
-      <expect label="returns FNREF as first item in sequence"
-              test="$x:result[ 1 ] = $fnref" />
+      <expect label="returns target reference as first item in
+                     sequence"
+              test="f:QName( $fnref )
+                      = f:QName( $x:result[ 1 ] )" />
 
       <expect label="returns arguments from both partial applications"
               test="count( $x:result ) = 3" />
@@ -406,7 +407,9 @@
 
 
     <!-- caller may extract the function ref from the sequence and
-         assert on that -->
+         assert on that; we are going to explicitly choose to *not*
+         support that behavior, since an fnref acquires meaning as an
+         opaque unit  -->
     <scenario label="given a valid fref, partially applied with N>0
                      arguments, without argument sequence">
       <call function="f:is-partial">
@@ -414,8 +417,8 @@
                select="f:partial( foo:ternary(), (1, 2) )[ 1 ]" />
       </call>
 
-      <expect label="returns true()"
-              test="$x:result = true()" />
+      <expect label="returns false()"
+              select="false()" />
     </scenario>
   </scenario>