From 4e987026148fe65c323afbc93cd560c07bf06b3f Mon Sep 17 00:00:00 2001
From: Yale AI Dept <ai@nebula.cs.yale.edu>
Date: Wed, 14 Jul 1993 13:08:00 -0500
Subject: Import to github.

---
 ast/tc-structs.scm | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 ast/tc-structs.scm

(limited to 'ast/tc-structs.scm')

diff --git a/ast/tc-structs.scm b/ast/tc-structs.scm
new file mode 100644
index 0000000..1433082
--- /dev/null
+++ b/ast/tc-structs.scm
@@ -0,0 +1,62 @@
+;;; These structures are used by the type checker for the internal
+;;; representation of type information.  These are referred to in
+;;; general as `ntype' structures.  Conversions are required between
+;;; ast types and ntypes.
+
+(define-struct ntype
+  (include ast-node))
+
+(define-struct ntycon
+  (include ntype)
+  (predicate ntycon?)
+  (slots
+   (tycon (type def))
+   (args (type (list ntype)))))
+
+(define-struct ntyvar
+  (include ntype)
+  (predicate ntyvar?)
+  (slots
+   ;; non-instantiated tyvars use #f for a value.
+   (value (type (maybe ntype)))
+   ;; could be encoded in value.
+   (context (type (list class)) (default ()))
+   (read-only? (type bool) (default #f) (bit #t))
+   (dict-params (type (list (tuple valdef (list (tuple class var))))))
+   ))
+
+;;; This is used only at the top level of a type during letrec type
+;;; checking.
+
+(define-struct recursive-type
+  (include ntype)
+  (predicate recursive-type?)
+  (slots
+   (type (type ntype))
+   (placeholders (type (list exp)))))
+
+;;; Gtypes are generalized types which can be copied quickly & stored in
+;;; interfaces.  They may contain monomorphic type variables which will not
+;;; be copied.
+
+(define-struct gtype
+  (include ntype)
+  (predicate gtype?)
+  (slots
+   (context (type (list (list class))))
+   (type (type ntype))))
+
+;;; These tyvars just index a list of pre-allocated tyvars.
+
+(define-struct gtyvar
+  (include ntype)
+  (predicate gtyvar?)
+  (slots
+   (varnum (type int))))
+
+(define-struct const-type
+  (include ntype)
+  (predicate const-type?)
+  (slots
+   (type (type ntype))))
+
-- 
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