Add basic c evaluator.

1 files changed, 34 insertions, 0 deletions

diff --git a/module/c/eval/environment.scm b/module/c/eval/environment.scm
new file mode 100644
index 00000000..12eefaf7
--- /dev/null
+++ b/module/c/eval/environment.scm
@@ -0,0 +1,34 @@
+(define-module (c eval environment)
+  :use-module (srfi srfi-1)
+  :export (make-environment
+           env-set! env-ref push-frame! pop-frame!))
+
+(define (make-frame)
+  (make-hash-table))
+
+(define (make-environment)
+  (list (make-frame)))
+
+;; Returns an updated environment, linear update
+(define (env-set! env key value)
+  ;; get handle to differentiate #f
+  ;; (even though #f should never be stored since it's not a C value)
+  (cond ((find (lambda (frame) (hashq-get-handle frame key)) env)
+         => (lambda (frame) (hashq-set! frame key value)))
+        (else (hashq-set! (car env) key value)))
+  env)
+
+(define (env-ref env key)
+  (cond ((null? env)
+         (scm-error 'misc-error "env-ref"
+                    "~s unbound"
+                    (list key)
+                    #f))
+        ((hashq-get-handle (car env) key) => cdr)
+        (else (env-ref (cdr env) key))))
+
+(define (push-frame! environment)
+  (cons (make-frame) environment))
+
+(define (pop-frame! environment)
+  (cdr environment))