Comment (by Erik Schnetter):

ANSI C preprocessors split the code into tokens and work on tokens. What C considers a token doesn’t work for Fortran.

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The notorious example is that it doesn’t preserve indentation (problem for fixed-format Fortran), or that “//” is string concatenation in Fortran, but introduces a comment in ANSI C, which then ignores the remainder of the line. Other problems come from how strings are quoted, or how numbers with scientific notion are denoted, or that Fortran uses the dot “.” to delimit operators (“x==2.or.x==3”, no floating-point constant in here).

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2363/make-cctk_looph-work-in-fortran-even-if-an