add base syntax-parameterize macro #210

README.md

@@ -8,7 +8,7 @@
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src/lips.js

@@ -7848,6 +7848,26 @@ var global_env = new Environment({
          and in the absence of syntax-parameterize, is functionally equivalent to
          define-syntax.`),
     // ------------------------------------------------------------------
+    'syntax-parameterize': doc(new Macro('syntax-parameterize', function(code, eval_args) {
+        const args = global_env.get('list->array')(code.car);
+        const env = this.inherit('syntax-parameterize');
+        while (args.length) {
+            const pair = args.shift();
+            if (!(is_pair(pair) || pair.car instanceof LSymbol)) {
+                const msg = `invalid syntax for syntax-parameterize: ${repr(code, true)}`;
+                throw new Error(`syntax-parameterize: ${msg}`);
+            }
+            const syntax = evaluate(pair.cdr.car, { ...eval_args, env: this });
+            typecheck('syntax-parameterize', syntax, 'syntax');
+            env.set(pair.car, new SyntaxParameter(syntax));
+        }
+        const body = new Pair(new LSymbol('begin'), code.cdr);
+        return evaluate(body, { ...eval_args, env });
+    }), `(syntax-parameterize (bindings) body)
+
+         Macro work similar to let-syntax but the the bindnds will be exposed to the user.
+         With syntax-parameterize you can define anaphoric macros.`),
+    // ------------------------------------------------------------------
     define: doc(Macro.defmacro('define', function(code, eval_args) {
         var env = this;
         if (code.car instanceof Pair &&

tests/syntax.scm

@@ -1382,3 +1382,13 @@
                                       e.message))
                           (match #/^return used outside of a lambda\^/)))
               #f)))
+
+(test "syntax: should create syntax-rules binding with syntax-parameterize"
+      (lambda (t)
+        (syntax-parameterize
+         ((it (syntax-rules ()
+                ((_) "hello")))
+          (is (syntax-rules ()
+                ((_) "world"))))
+         (t.is (string-append (it) " " (is))
+               "hello world"))))