trace special form. close #45

src/kiss/Prelude.hx

@@ -398,12 +398,17 @@ class Prelude {
 
     public static var printStr:(String) -> Void = _printStr;
 
-    public static function print<T>(v:T, label = ""):T {
+    public static function withLabel(v:Any, label = "") {
         var toPrint = label;
         if (label.length > 0) {
             toPrint += ": ";
         }
         toPrint += Std.string(v);
+        return toPrint;
+    }
+
+    public static function print<T>(v:T, label = ""):T {
+        var toPrint = withLabel(v, label);
         printStr(toPrint);
         return v;
     }

src/kiss/SpecialForms.hx

@@ -449,6 +449,22 @@ class SpecialForms {
             ECast(e, t).withMacroPosOf(wholeExp);
         }
 
+        k.doc("trace", 1, 2, "(trace <value> <?label>)");
+        map["trace"] = (wholeExp:ReaderExp, exps:Array<ReaderExp>, k:KissState) -> {
+            var b = wholeExp.expBuilder();
+            var label = if (exps.length > 1) exps[1] else b.str("");
+            var label = k.convert(label);
+            EBlock([
+                EVars([
+                    toVar(b.symbol("v"), exps[0], k)
+                ]).withMacroPosOf(wholeExp),
+                ECall(EConst(CIdent("trace")).withMacroPosOf(wholeExp), [
+                    macro kiss.Prelude.withLabel(v, $label)
+                ]).withMacroPosOf(wholeExp),
+                k.convert(exps[0])
+            ]).withMacroPosOf(wholeExp);
+        };
+
         return map;
     }
     

src/test/cases/BasicTestCase.hx

@@ -346,6 +346,10 @@ class BasicTestCase extends Test {
     function testWhileLet() {
         _testWhileLet();
     }
+
+    function testTrace() {
+        _testTrace();
+    }
 }
 
 class BasicObject {

src/test/cases/BasicTestCase.kiss

@@ -637,4 +637,7 @@ From:[(assert false (+ \"false \" \"should \" \"have \" \"been \" \"true\"))]" m
             stream (Stream.fromString "a\nb\nc")]
         (whileLet [(Some line) (stream.takeLine)]
             (Assert.equals (nth lines idx) line)
-            (+= idx 1))))
+            (+= idx 1))))
+
+(function _testTrace []
+    (Assert.equals 5 (trace 5 "num")))