> On May 13, 2020, at 17:42, John P. Linderman <jpl.jpl@gmail.com> wrote:
>
> I never liked call by reference. When I was trying to understand a chunk of code, it was a great mental simplification to know that whatever a called routine did, it couldn't have an effect on the code I was trying to understand except through a returned value and (ghastly) global variables. ...

A Fortran implementation I used years ago kept constants in a "literal pool".  So, if you called a subroutine, passing in a constant, there was a possibility that the constant might be modified upon the routine's return.  I don't recall this ever causing a problem in practice, but the possibility was amusing...