fix firstArg behavior in BinaryOpUGen by a list-approved hack

git-svn-id: https://supercollider.svn.sourceforge.net/svnroot/supercollider/trunk@10293 a380766d-ff14-0410-b294-a243070f3f08

common/build/SCClassLibrary/Common/Audio/BasicOpsUGen.sc

@@ -15,9 +15,15 @@ BasicOpUGen : UGen {
 //	}
 	operator_ { arg op;
 		operator = op;
-		specialIndex = operator.specialIndex;
-			// 'firstArg' check is necessary for audio-rate Demand units
-		if(specialIndex < 0 and: { operator != 'firstArg' }) {
+			// 'firstArg' exists in the server
+			// but the 'specialIndex' primitive doesn't report the right value
+			// admittedly this is a hack, but the hack was approved on sc-dev
+		if(operator == 'firstArg') {
+			specialIndex = 46
+		} {
+			specialIndex = operator.specialIndex;
+		};
+		if(specialIndex < 0) {
 			Error("Operator '%' applied to a UGen is not supported in scsynth".format(operator)).throw
 		}
 	}