fix eq? for strings

rt/rt.mjs

@@ -60,6 +60,8 @@ function schemeToJS(x, map) {
         return x;
     case 'object':
         if (x instanceof String) {
+            if (x.charAt(0) === 's')
+                return x.substring(1);
             return x.substring(2);
         }
         if (x instanceof Pair) {
@@ -124,15 +126,17 @@ function rt(engine) {
         // that's not specified on the Scheme language level.  Using JS
         // strings for symbols allows us to compare with ===, as is
         // required.
-        'string?': x => typeof(x) === 'string' && x.charAt(0) === 's',
+        'string?': x => (typeof x === 'string' || x instanceof String)
+                     && x.charAt(0) === 's',
         '%symbol?': x => typeof(x) === 'string' && x.charAt(0) === 'S',
+        '%string=?' : (x, y) => x.valueOf() === y.valueOf(),
 
         // The code still wants to access chars as a list.
         '%list->string': chars => {
             let ret = 's';
             for (; chars != null; chars = chars.cdr)
                 ret += String.fromCharCode(chars.car >>> 1);
-            return ret;
+            return new String (ret);
         },
         '%string->list': x => {
             let ret = null;
@@ -146,7 +150,7 @@ function rt(engine) {
 
         // Gensyms are instances of String (objects with identity).
         '%make-gensym': str => new String('S' + str),
-        '%gensym?': x => x instanceof String,
+        '%gensym?': x => x instanceof String && x.charAt(0) === 'S',
 
         'cons': (car, cdr) => new Pair(car, cdr),
         'pair?': x => x instanceof Pair,

scheme-lib/rnrs.ss

@@ -177,8 +177,7 @@
             (%unreachable))
     (%string->list s))
   (define (string=? s1 s2)
-    ;; This is ok because strings are currently represented as javascript values.
-    (eq? s1 s2))
+    (%string=? s1 s2))
   (define (string->symbol s)
     (if (string? s)
         (%string->symbol s)

schism/compiler.ss

@@ -87,6 +87,7 @@
 
       (bool string? (scm x))
       (bool %symbol? (scm x))
+      (bool %string=? (scm x) (scm y))
 
       (scm %list->string (scm x))
       (scm %string->list (scm x))
@@ -542,7 +543,7 @@
                    eq? number? char?
                    %make-number %make-char
                    %number-value %char-value
-                   string? %symbol?
+                   string? %symbol? %string=?
                    %list->string %string->list
                    %string->symbol %symbol->string
                    %make-gensym %gensym?

test/string-eq.ss

@@ -0,0 +1,25 @@
+;; Copyright 2019 Google LLC
+;;
+;; Licensed under the Apache License, Version 2.0 (the License);
+;; you may not use this file except in compliance with the License.
+;; You may obtain a copy of the License at
+;;
+;;     http://www.apache.org/licenses/LICENSE-2.0
+;;
+;; Unless required by applicable law or agreed to in writing, software
+;; distributed under the License is distributed on an AS IS BASIS,
+;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;; See the License for the specific language governing permissions and
+;; limitations under the License.
+
+(library
+    (trivial)
+  (export do-test)
+  (import (rnrs))
+
+  (define (do-test)
+    (let* ((x (list->string '(#\a #\b #\c)))
+           (y (string->symbol x)))
+      (and (not (eq? x (list->string '(#\a #\b #\c))))
+           (eq? x x)
+           (eq? (symbol->string y) (symbol->string y))))))