Implement and test explicate-control

.editorconfig

@@ -1,3 +1,4 @@
 [*.scm]
 indent_style = space
 indent_size = 2
+trim_trailing_whitespace = true

explicate-control.scm

@@ -0,0 +1,29 @@
+#lang racket
+
+(require racket/fixnum)
+
+(provide explicate-control)
+
+(define (explicate-control sexp)
+  (match sexp
+    [`(program ,info ,exp)
+      `(program ,info ,(explicate-control-tail exp))]))
+
+; after a remove-complex-opera*, all expressions
+; are compatible with C0
+(define (explicate-control-tail exp)
+  (match exp
+    [(? fixnum?) `(return ,exp)]
+    [(? symbol?) `(return ,exp)]
+    [`(read) `(return ,exp)]
+    [`(- ,e) `(return ,exp)]
+    [`(+ ,e1 ,e2) `(return ,exp)]
+    [`(let ([,var ,rexp]) ,body)
+     (explicate-control-assign var rexp (explicate-control-tail body))]))
+
+; stmt :=  (assign var exp)
+; tail :=  (return exp) / (seq stmt tail)
+(define (explicate-control-assign var exp c0-body) `()
+  (match exp
+     [`(let ([,v ,x]) ,b) (explicate-control-assign v x (explicate-control-assign var b c0-body))]
+     [_ `(seq (assign ,var ,exp) ,c0-body)]))

test-explicate-control.scm

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+#lang racket
+
+(require "test-util.scm")
+(require "remove-complex-oper.scm")
+(require "explicate-control.scm")
+(require "c2.scm")
+
+(define programs 
+  (list
+   `(program () (+ 2 3))
+   `(program () (+ (- 2) 3))
+   `(program ()
+             (let ([y (let ([x 20])
+                        (+ x (let ([x 22]) x)))]) y))
+   `(program ()
+      (let ([a 42])
+        (let ([b a])
+          b)))
+
+   `(program () (+ (let ([x (+ (- 1) 2)]) (+ x 2)) (+ 4 5)))))
+
+      
+
+(define (pass program) (explicate-control (remove-complex-opera* program)))
+
+(test-eq
+ (pass (list-ref programs 0))
+ `(program ()
+           (return (+ 2 3))))
+
+(test-eq
+ (pass (list-ref programs 1))
+ `(program ()
+           (seq (assign tmp.1 (- 2))
+             (return (+ tmp.1 3)))))
+
+(test-eq
+  (pass (list-ref programs 2))
+  `(program ()
+     (seq (assign x.1 20)
+      (seq (assign x.2 22)
+       (seq (assign y.1 (+ x.1 x.2))
+        (return y.1))))))
+
+(test-eq
+ (pass (list-ref programs 3))
+ `(program ()
+           (seq (assign a.1 42)
+                (seq (assign b.1 a.1)
+                     (return b.1)))))
+
+(test-eq
+ (pass (list-ref programs 4))
+ `(program ()
+           (seq (assign tmp.1 (- 1)) 
+                (seq (assign x.1 (+ tmp.1 2)) 
+                     (seq (assign tmp.2 (+ x.1 2)) 
+                          (seq (assign tmp.3 (+ 4 5)) 
+                               (return (+ tmp.2 tmp.3))))))))