Re: [help-texinfo] Mathematical Fractions

[Gavin Smith]

On 14 February 2017 at 19:17, Gavin Smith <address@hidden> wrote:
> except for a warning "warning: @iftex should only appear at the
> beginning of a line (possibly involving @Frac)" that you may get with
> texi2any.

Of course, another option is to interchange the macro and conditional:

@iftex
@macro Frac{a,b}
@math{\a\ \\over \b\}
@end macro
@end iftex
@ifnottex
@macro Frac{a,b}
\a\ / \b\
@end macro
@end ifnottex

c divided by d is written as @Frac{c,d}.