From ab36cad95b9b70a7cb9c5ff8cc654801023a3aaf Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Mon, 6 Feb 2023 18:30:47 -0500
Subject: Remove (var ...) intermediate form.

---
 chickadee/graphics/seagull.scm | 27 +++++++++++----------------
 1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/chickadee/graphics/seagull.scm b/chickadee/graphics/seagull.scm
index 5cacdcf..fdd1487 100644
--- a/chickadee/graphics/seagull.scm
+++ b/chickadee/graphics/seagull.scm
@@ -257,10 +257,7 @@
   (map (lambda (exp) (expand exp stage env)) exps))
 
 (define (expand:variable exp stage env)
-  ;; Replace original variable with alpha-converted name, but keep
-  ;; track of the original for showing the user error messages that
-  ;; make sense later.
-  `(var ,(lookup exp env) ,exp))
+  (lookup exp env))
 
 (define (expand:if predicate consequent alternate stage env)
   `(if ,(expand predicate stage env)
@@ -577,8 +574,8 @@
 (define (propagate-constants exp env)
   (match exp
     ((? immediate?) exp)
-    (('var name _)
-     (or (lookup* name env) exp))
+    ((? symbol?)
+     (or (lookup* exp env) exp))
     (('if predicate consequent alternate)
      (propagate:if predicate consequent alternate env))
     (('lambda (params ...) body)
@@ -629,14 +626,14 @@
   (match exp
     ((? immediate?)
      #t)
-    (('var name original-name)
-     (or (memq name bound-vars) ; bound vars: OK
-         (memq name top-level-vars) ; top-level vars: OK
+    ((? symbol?)
+     (or (memq exp bound-vars) ; bound vars: OK
+         (memq exp top-level-vars) ; top-level vars: OK
          ;; Free variables that aren't top-level are not allowed because
          ;; GLSL doesn't support closures.
          (raise-exception
           (make-exception
-           (make-seagull-scope-error original-name)
+           (make-seagull-scope-error exp)
            (make-exception-with-origin check-free-variables)
            (make-exception-with-message
             "seagull: free variable is not top-level")
@@ -752,7 +749,7 @@
 
 (define (hoist-functions exp)
   (match exp
-    ((or (? immediate?) ('var _ _))
+    ((or (? immediate?) (? symbol?))
      (values exp (empty-env)))
     (('if predicate consequent alternate)
      (hoist:if predicate consequent alternate))
@@ -1409,10 +1406,8 @@
      (append (free-variables-in-type struct)
              (free-variables-in-type var)))))
 
-;; Quantified variables:
-;; - Unused parameters
-;; - Parameters that appear free in the return type
-;; - Parameters that are used in overloaded primcalls
+;; Quantified variables are type variables that appear free in the
+;; function return types or in the predicate.
 (define (generalize type pred env)
   (if (function-type? type)
       (match (difference (delete-duplicates
@@ -1797,7 +1792,7 @@
   (match exp
     ((? immediate?)
      (infer:immediate exp))
-    ((or (? symbol? name) ('var name _))
+    ((? symbol? name)
      (infer:variable name env))
     (('if predicate consequent alternate)
      (infer:if predicate consequent alternate env))
-- 
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