Index: polemy/eval.d
==================================================================
--- polemy/eval.d
+++ polemy/eval.d
@@ -70,10 +70,13 @@
 		if( auto ft = cast(FunValue)args[1] )
 		if( auto fe = cast(FunValue)args[2] )
 			return (x.data == 0 ? fe : ft).call(pos,lay,[]);
 		throw genex!RuntimeException(pos, "type mismatch in if");
 	}));
+	ctx.set("_isint", "@v", native( (Value v){return new IntValue(BigInt(cast(IntValue)v is null ? 0 : 1));} ));
+	ctx.set("_isstr", "@v", native( (Value v){return new IntValue(BigInt(cast(StrValue)v is null ? 0 : 1));} ));
+	ctx.set("_isfun", "@v", native( (Value v){return new IntValue(BigInt(cast(FunValue)v is null ? 0 : 1));} ));
 	return ctx;
 }
 
 /// Entry point of this module