Bug 15480 – std.algorithm.iteration.map not accepting multiple lambdas

The map function in std.algorithm.iteration only accepts strings with "a" as the variable name for multiple functions at https://dlang.org/phobos/std_algorithm_iteration.html#.map . The following code doesn't work with two lambdas being passed to map as follows : Program import std.algorithm.iteration : map; import std.algorithm.comparison : equal; import std.range : chain; void main() { int[] arr1 = [ 1, 2, 3, 4 ]; int[] arr2 = [ 5, 6 ]; auto dd = map!(z => z * z, c => c * c * c)(chain(arr1, arr2)); } Output : /usr/include/dmd/phobos/std/meta.d(546): Error: template instance F!(__lambda1) cannot use local '__lambda1' as parameter to non-global template AppliedReturnType(alias f) /usr/include/dmd/phobos/std/meta.d(552): Error: template instance maps_square.main.staticMap!(AppliedReturnType, __lambda1) error instantiating /usr/include/dmd/phobos/std/algorithm/iteration.d(447): instantiated from here: staticMap!(AppliedReturnType, __lambda1, __lambda2) maps_square.d(11): instantiated from here: map!(Result) /usr/include/dmd/phobos/std/meta.d(546): Error: template instance F!(__lambda2) cannot use local '__lambda2' as parameter to non-global template AppliedReturnType(alias f) /usr/include/dmd/phobos/std/meta.d(553): Error: template instance maps_square.main.staticMap!(AppliedReturnType, __lambda2) error instantiating /usr/include/dmd/phobos/std/algorithm/iteration.d(447): instantiated from here: staticMap!(AppliedReturnType, __lambda1, __lambda2) maps_square.d(11): instantiated from here: map!(Result) The same program when replaced with mixins instead of functions with variable name as "a" works Program : import std.algorithm.iteration : map; import std.algorithm.comparison : equal; import std.range : chain; void main() { int[] arr1 = [ 1, 2, 3, 4 ]; int[] arr2 = [ 5, 6 ]; auto dd = map!("a * a", "a * a * a")(chain(arr1, arr2)); } The relevant discussion at dlang learn forum at http://forum.dlang.org/thread/[email protected] I tried reading the source https://github.com/D-Programming-Language/phobos/blob/master/std/algorithm/iteration.d#L520 .Some hint that "a" should be used at https://github.com/D-Programming-Language/phobos/blob/master/std/functional.d#L101. It will be helpful to specify lambdas instead of mixins with "a" variable names as they are more readable and elegant. The workaround was to use tuples in the forum. I am d beginner and any thoughts on confirming this as a bug will be helpful. System information : OS : Linux Mint 15 (64 bit) DMD version : DMD64 D Compiler v2.069.2

I took a local copy of the std.algorithm.iteration as myiteration.d and used it for debugging. Commenting out the following two lines make this work https://github.com/D-Programming-Language/phobos/blob/master/std/algorithm/iteration.d#L461-L463. I don't know why that fails.

Seems this depends upon https://issues.dlang.org/show_bug.cgi?id=5710. Atleast can this assert be removed or replaced by some other logic to check for void functions?

Seems related : https://github.com/D-Programming-Language/phobos/pull/1917

Fix: https://github.com/D-Programming-Language/phobos/pull/3969

Commits pushed to master at https://github.com/D-Programming-Language/phobos https://github.com/D-Programming-Language/phobos/commit/b23608b63523dc8603764cfcff86482abd11b841 Fix Phobos issue 15480 https://github.com/D-Programming-Language/phobos/commit/6bb36bf522b7336dd41873bb4f1a2df57b90f7fc Merge pull request #3969 from tsbockman/issue_15480 Fix Phobos issue 15480

Commits pushed to stable at https://github.com/D-Programming-Language/phobos https://github.com/D-Programming-Language/phobos/commit/b23608b63523dc8603764cfcff86482abd11b841 Fix Phobos issue 15480 https://github.com/D-Programming-Language/phobos/commit/6bb36bf522b7336dd41873bb4f1a2df57b90f7fc Merge pull request #3969 from tsbockman/issue_15480