miniscm: add better support for immutable strings, and refactor to use real strings

2 files changed, 27 insertions, 5 deletions

diff --git a/miniscm/init.scm b/miniscm/init.scm
index 1803388..725c7d0 100644
--- a/miniscm/init.scm
+++ b/miniscm/init.scm
@@ -90,10 +90,10 @@
 
 ;;; Emulation of mutable strings.
 
-(define string-ref list-ref)
-(define string-set! list-set!)
-(define string list)
-(define (string->list x) x)
+(define mutable-string-ref list-ref)
+(define mutable-string-set! list-set!)
+(define mutable-string list)
+(define (mutable-string->list x) x)
 
 (define list<=>
   (lambda (x y <=>)
@@ -139,6 +139,18 @@
       ((f (car l)) #t)
       (else (any f (cdr l))))))
 
+(define string->list
+  (lambda (str)
+    (let ((len (string-length str)))
+      (letrec ((loop
+                (lambda (i lst)
+                  (if (= i len)
+                      (reverse lst)
+                      (loop (+ i 1)
+                            (cons (string-ref str i)
+                                  lst))))))
+        (loop 0)))))
+
 (macro
  cond-expand
  (lambda (body)
diff --git a/miniscm/miniscm.c b/miniscm/miniscm.c
index e2b062d..7500ad2 100644
--- a/miniscm/miniscm.c
+++ b/miniscm/miniscm.c
@@ -1216,6 +1216,7 @@ register pointer a, b;
 
 #define OP_CHAR2INT             111
 #define OP_STRINGREF            112
+#define OP_STRINGLEN            113
 
 static FILE *tmpfp;
 static int tok;
@@ -1977,6 +1978,13 @@ register short op;
 		}
 
 		s_return(mk_char_c(strvalue(x)[ivalue(y)]));
+
+	case OP_STRINGLEN:
+		if (!isstring(car(args))) {
+			Error_0("string-length -- argument must be string");
+		}
+
+		s_return(mk_number(strlen(strvalue(car(args)))));
 	}
 }
 
@@ -2481,7 +2489,8 @@ pointer	(*dispatch_table[])() = {
 	opexe_7,        /* OP_WRITEOUT */
 
 	opexe_2,        /* OP_CHAR2INT */
-	opexe_4         /* OP_STRINGREF */
+	opexe_4,        /* OP_STRINGREF */
+	opexe_4         /* OP_STRINGLEN */
 };
 
 
@@ -2642,6 +2651,7 @@ init_procs()
 	mk_proc(OP_CHAR2INT, "char->integer");
 
 	mk_proc(OP_STRINGREF, "string-ref");
+	mk_proc(OP_STRINGLEN, "string-length");
 }