Bruce HartwegDonal K. Fellows$Revision: 1.3 $

This TIP proposes altering the [regsub] command so that it can return the substituted string as the result of the command.

In many of the most common uses of the [regsub] command, the substituted string is used only once in the immediately following command. However, the [regsub] command only provides the substituted string via a variable, with the result of the command itself being the number of substitutions performed. For many uses of the command, it is the substituted string though that is the most useful result, especially if some other transformation is going to be applied to it (like further [regsub] commands or some other Tcl command like one of the [string] subcommands or [subst].) This TIP proposes a mechanism for providing the ability to return the string as the command's result, and in a way that is backward-compatible with existing scripts.

ICAgcmVnc3ViID9zd2l0Y2hlcz8gZXhwIHN0cmluZyBzdWJTcGVjID92YXJOYW1lPw== If varName is supplied the new string is written there and the number of substitutions are returned (same as current behavior). If varName is not supplied than the new string is returned as the result of the [regsub] command.

This is a pretty easy change, although I do not currently have an environment where I can actually build and test this the following should create the desired behavior. File: tcl/generic/tclCmdMZ.c Function: Tcl_RegsubObjCmd Currently (v 1.52): ICAgIGlmIChvYmpjIC0gaWR4ICE9IDQpIHs=CSBUY2xfV3JvbmdOdW1BcmdzKGludGVycCwgMSwgb2Jqdiw=CQkgIj9zd2l0Y2hlcz8gZXhwIHN0cmluZyBzdWJTcGVjIHZhck5hbWUiKTs=CSByZXR1cm4gVENMX0VSUk9SOw==ICAgIH0= which should be changed to: ICAgIG9iamMgLT0gaWR4Ow==ICAgIGlmIChvYmpjICE9IDMgfHwgb2JqYyAhPSA0KSB7CSBUY2xfV3JvbmdOdW1BcmdzKGludGVycCwgMSwgb2Jqdiw=CQkgIj9zd2l0Y2hlcz8gZXhwIHN0cmluZyBzdWJTcGVjID92YXJOYW1lPyIpOw==CSByZXR1cm4gVENMX0VSUk9SOw==ICAgIH0= and then at the end change this: ICAgIGlmIChUY2xfT2JqU2V0VmFyMihpbnRlcnAsIG9ianZbM10sIE5VTEwsIHJlc3VsdFB0ciwgMCkgPT0gTlVMTCkgew==CSBUY2xfQXBwZW5kUmVzdWx0KGludGVycCwgImNvdWxkbid0IHNldCB2YXJpYWJsZSBcIiIsCQkgVGNsX0dldFN0cmluZyhvYmp2WzNdKSwgIlwiIiwgKGNoYXIgKikgTlVMTCk7CSByZXN1bHQgPSBUQ0xfRVJST1I7ICAgIH0gZWxzZSB7CSAvKg==CSAgKiBTZXQgdGhlIGludGVycHJldGVyJ3Mgb2JqZWN0IHJlc3VsdCB0byBhbiBpbnRlZ2VyIG9iamVjdA==CSAgKiBob2xkaW5nIHRoZSBudW1iZXIgb2YgbWF0Y2hlcy4=CSAgKi8=CSBUY2xfU2V0SW50T2JqKFRjbF9HZXRPYmpSZXN1bHQoaW50ZXJwKSwgbnVtTWF0Y2hlcyk7ICAgIH0= to this: ICAgIGlmIChvYmpjID09IDQpIHs=ICAgICAgICBpZiAoVGNsX09ialNldFZhcjIoaW50ZXJwLCBvYmp2WzNdLCBOVUxMLCByZXN1bHRQdHIsIDApID09IE5VTEwpIHs=ICAgICAgICAgICAgVGNsX0FwcGVuZFJlc3VsdChpbnRlcnAsICJjb3VsZG4ndCBzZXQgdmFyaWFibGUgXCIiLA==ICAgICAgICAJICAgICBUY2xfR2V0U3RyaW5nKG9ianZbM10pLCAiXCIiLCAoY2hhciAqKSBOVUxMKTs=ICAgICAgICAgICAgcmVzdWx0ID0gVENMX0VSUk9SOw==ICAgICAgICB9IGVsc2Ugew==ICAgICAgICAgICAgLyo=ICAgICAgICAgICAgICogU2V0IHRoZSBpbnRlcnByZXRlcidzIG9iamVjdCByZXN1bHQgdG8gYW4gaW50ZWdlciBvYmplY3Q=ICAgICAgICAgICAgICogaG9sZGluZyB0aGUgbnVtYmVyIG9mIG1hdGNoZXMuICAgICAgICAgICAgICovICAgICAgICAgICAgVGNsX1NldEludE9iaihUY2xfR2V0T2JqUmVzdWx0KGludGVycCksIG51bU1hdGNoZXMpOw==ICAgICAgICB9ICAgIH0gZWxzZSB7ICAgICAgICAgICAvKg==ICAgICAgICAgICAgKiBObyB2YXJuYW1lIHN1cHBsaWVkLCByZXR1cm4gc3RyaW5nIGFzIHJlc3VsdA==ICAgICAgICAgICAgKi8=ICAgICAgICAgICBUY2xfU2V0T2JqUmVzdWx0KGludGVycCwgcmVzdWx0UHRyKTs=ICAgIH0= And then minor updates to the man page to show that varName is optional.

This document has been placed in the public domain.