Implement ?: operator

Question

Implement ?: operator

boeckmann opened this issue a year ago · comments

expr ?: default returns expr, if it is defined. It returns default, if expr is not defined Makes the following convinient:

BORDER_COLOR = BORDER_COLOR ?: 6

Bernd Böckmann · Answer 1 · Wed Apr 26 2023 04:47:59 GMT+0800 (China Standard Time)

While this is nice it is nothing that can not be done with an .IFNDEF. Also it is not so common.

Fred N. van Kempen · Answer 2 · Wed Apr 26 2023 04:49:11 GMT+0800 (China Standard Time)

Hahaha! This gives opportunity to some fun: FOO = C64 ?: APPLE2 ?: $DEAD .echo "Haha, foo is ",[$]FOO On the commandline, with a -DC64=100 and/or -DAPPLE2=2 you can create fun output. For real use, this could be used to "get" the type of target into a single variable, based on what target was -D'd on the commandline..

Bernd Böckmann · Answer 3 · Wed Apr 26 2023 04:55:16 GMT+0800 (China Standard Time)

Yeah, it has some nice characteristics. Do you think its useful? Would prevent some IF cascades. I am in doubt if it is worth implementing.

Fred N. van Kempen · Answer 4 · Wed Apr 26 2023 05:01:12 GMT+0800 (China Standard Time)

It is already implemented - the expressions are iterative, so it does not matter if you use it once or 10 times in a single statement. It is like foo = (..) ? x : (..) ? y : (..) ? z : -1 in C. Gets tedious, but does work and saves a LOT of "iffing".