On Saturday, January 27, 2024 3:33 PM, Paul Smith wrote: >On Mon, 2024-01-22 at 08:15 -0500, Paul Smith wrote: >> Let's step back and I'll try to think more clearly about this. > >Sorry for the delay in replying. > >I can see that I was thinking about this one way but there's another way to >look at it >that I didn't think of. We are talking only about >(a) append operators _other than_ +=, and (b) situations where the variable >already >has a value when the append operator is parsed. > >In all cases we would expand the right-hand side of the variable according to >the >assignment operator: e.g., if it were +:= we would immediately expand the RHS. > >My proposal was to keep the type of variable (recursive vs. simple) the same >and >then "fix up" the result of the RHS so it could be appended in a correct way. >In this >conception the operator applies ONLY to the RHS value, and will set the type >of the >variable only if the variable doesn't already exist, as a side-effect. > >The other way to think about it is that the assignment operator overrides the >type >of the variable as well: we would re-evaluate the LHS value then append the >RHS. >E.g., if it were +:= we would immediately expand the RHS as well and change the >type of simple. In this conception the operator resets the type of the >variable as its >primary function, not just as a side-effect, and modifies not just the RHS >value but >also (possibly) the LHS value as well. > >An example to make this clearer: > >Given: > > foo = 1 > bar = $(foo) > foo = 2 > bar +:= $(foo) > foo = 3 > bar += $(foo) > > $(info bar=$(bar)) > >In my original version, the result would be that "bar" is a recursive variable >with the >value "$(foo) 2 $(foo)" and the output of the info function would be "bar=3 2 >3". > >In the alternative version, the result would be that "bar" is a simple >variable with the >value "2 2 3" and the output of the info function would obviously be "bar=2 2 >3". > >I'm interested in peoples' opinions about which of these two implementations >they >would feel to be more "intuitive" or "correct". >Also please consider issues of "action at a distance" where a variable is >assigned in >one makefile and appended to in some other makefile, potentially far away. > > >This discussion has really helped me crystallize the differences and should >make the >resulting documentation, if/when it's written, much more clear so I definitely >appreciate it!
Intuitive reading of this would seem that "bar=2 2 3" is better, as +:= should force complete resolution of the string applied to bar, not partial resolution of foo keeping an instance of $(foo) for resolution later. Just my $0.02. Randall
