Comment by pklausler
3 months ago
Note that Fortran's interpretation of the term "pure" bizarrely allows a "pure" subprogram to depend on mutable state elsewhere (in a host, a module, or a COMMON block). So Fortran's "pure" functions aren't referentially transparent.
(F'2023 added a stronger form of "pure" and calls it "simple", but it didn't strengthen the places where a "pure" procedure should be required to be "simple", such as DO CONCURRENT, so being "simple" will be its own reward, if any compiler actually implements it. And a "simple" function's result value can still depend on a mutable pointer target.)
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