(once) and (oncePerInstance)

src/kiss/Helpers.hx

@@ -9,7 +9,9 @@ import kiss.Reader;
 import kiss.CompileError;
 import kiss.Kiss;
 import kiss.SpecialForms;
+import uuid.Uuid;
 
+using uuid.Uuid;
 using tink.MacroApi;
 using kiss.Reader;
 using kiss.Helpers;
@@ -364,6 +366,7 @@ class Helpers {
             list: (exps:Array<ReaderExp>) -> ListExp(exps).withPosOf(posRef),
             str: (s:String) -> StrExp(s).withPosOf(posRef),
             symbol: (name:String) -> Symbol(name).withPosOf(posRef),
+            gensym: () -> Symbol('_${Uuid.v4().toShort()}').withPosOf(posRef),
             raw: (code:String) -> RawHaxe(code).withPosOf(posRef),
             typed: (path:String, exp:ReaderExp) -> TypedExp(path, exp).withPosOf(posRef),
             meta: (m:String, exp:ReaderExp) -> MetaExp(m, exp).withPosOf(posRef),

src/kiss/Macros.hx

@@ -2,12 +2,10 @@ package kiss;
 
 import haxe.macro.Expr;
 import haxe.macro.Context;
-import uuid.Uuid;
 import kiss.Reader;
 import kiss.Kiss;
 import kiss.CompileError;
 
-using uuid.Uuid;
 using kiss.Kiss;
 using kiss.Reader;
 using kiss.Helpers;
@@ -178,8 +176,8 @@ class Macros {
         macros["or"] = (wholeExp:ReaderExp, args:Array<ReaderExp>, k) -> {
             wholeExp.checkNumArgs(2, null, "(or [v1] [v2] [values...])");
             var b = wholeExp.expBuilder();
-            var uniqueVarName = "_" + Uuid.v4().toShort();
-            var uniqueVarSymbol = b.symbol(uniqueVarName);
+
+            var uniqueVarSymbol = b.gensym();
 
             b.begin([
                 b.call(b.symbol("deflocal"), [
@@ -204,8 +202,8 @@ class Macros {
         macros["and"] = (wholeExp:ReaderExp, args:Array<ReaderExp>, k) -> {
             wholeExp.checkNumArgs(2, null, "(and [v1] [v2] [values...])");
             var b = wholeExp.expBuilder();
-            var uniqueVarName = "_" + Uuid.v4().toShort();
-            var uniqueVarSymbol = b.symbol(uniqueVarName);
+            
+            var uniqueVarSymbol = b.gensym();
 
             var condCases = [
                 for (arg in args) {
@@ -552,8 +550,20 @@ class Macros {
             wholeExp.checkNumArgs(1, 1, "(collect [iterator or iterable])");
             var b = wholeExp.expBuilder();
             b.call(b.symbol("for"), [b.symbol("elem"), exps[0], b.symbol("elem")]);
+        };
+
+        function once(macroName:String, wholeExp:ReaderExp, exps:Array<ReaderExp>, k:KissState) {
+            wholeExp.checkNumArgs(1, null, '($macroName [body...])');
+            var b = wholeExp.expBuilder();
+            var flag = b.gensym();
+            // define the field:
+            k.convert(b.call(b.symbol(macroName), [b.meta("mut", flag), b.symbol("true")]));
+            return b.call(b.symbol("when"), [flag, b.call(b.symbol("set"), [flag, b.symbol("false")])].concat(exps));
         }
 
+        macros["once"] = once.bind("defvar");
+        macros["oncePerInstance"] = once.bind("defprop");
+
         return macros;
     }
 

src/test/cases/OnceTestCase.hx

@@ -0,0 +1,17 @@
+package test.cases;
+
+import utest.Test;
+import utest.Assert;
+import kiss.Prelude;
+
+class OnceTestCase extends Test {
+    function testOnce() {
+        new OnceTestObject();
+        new OnceTestObject();
+        Assert.equals(1, OnceTestObject.staticCount);
+        Assert.equals(2, OnceTestObject.instanceCount);
+    }
+}
+
+@:build(kiss.Kiss.build("OnceTestObject.kiss"))
+class OnceTestObject {}

src/test/cases/OnceTestObject.kiss

@@ -0,0 +1,8 @@
+(defvar &mut staticCount 0)
+(defvar &mut instanceCount 0)
+
+(defmethod new []
+    (once
+        (+= staticCount 1))
+    (oncePerInstance
+        (+= instanceCount 1)))