(default <var> <value>)

src/kiss/Macros.hx

@@ -1598,6 +1598,13 @@ class Macros {
 
             b.let([b.typed('Array<${typeName}>', arraySymbol), b.list([])], [for (arg in args.slice(1)) b.call(b.field("push", arraySymbol), [arg])].concat([arraySymbol]));
         };
+
+        k.doc("default", 2, 2, "(default <variable> <value>)");
+        macros["default"] = (wholeExp:ReaderExp, args:Array<ReaderExp>, k:KissState) -> {
+            var b = wholeExp.expBuilder();
+            b.when(b.callSymbol("isNull", [args[0]]), [b.set(args[0], args[1])]);
+        };
+
         return macros;
     }
 

src/test/cases/BasicTestCase.hx

@@ -477,5 +477,9 @@ class BasicTestCase extends Test {
         _testTypedArrayMacro();
     }
     
+    function testDefault() {
+        _testDefault();
+    }
+    
     var aNullToPrint = null;
 }

src/test/cases/BasicTestCase.kiss

@@ -1015,3 +1015,18 @@ From:[(assert false (+ \"false \" \"should \" \"have \" \"been \" \"true\"))]" m
     (let [a (array Float 1 1.5 2)]
         (Assert.isTrue (Std.isOfType a Array))
         (Assert.isTrue (Std.isOfType (first a) Float))))
+                        
+(function _testDefault []
+    // TODO it would be nice to allow &mut on the whole list and &final to override it
+    (let [&mut f false
+                &mut t true
+                &mut n null
+                &mut i 5]
+        (default f true)
+        (Assert.equals false f )
+        (default t false)
+        (Assert.equals true t)
+        (default n 5)
+        (Assert.equals 5 n)
+        (default i 9)
+        (Assert.equals i 5)))