Re: Comprehension problem with macros

[Ralph Corderoy]

Hi Oliver,

> .nr number 0 1
> .while (\n[number] < 16) \{\
> .ie (\n[number] < 10) \[u4E0\n[number]]
> .el \[u4E0\*[\n[number]]]
> .nr number +1
> .\}
>
> So far, everything works perfectly.
>
> However, if I wrap this loop in a macro like
>
> .de myline
> .\" material as above
> ..

The text after .de is read twice.  Once when the macro is defined and
again when it is executed.  The reading occurs in two different modes.
See section 7 of CSTR 54.  https://troff.org/54.pdf

For example, \nn puts the value of number-register n when the macro is
defined into the macro whereas \\nn delays getting the value of n to
when the macro is executed.

Here's a variation on your test.

    $ cat oliver.tr
    .pl 2
    .
    .ds 0 0
    .ds 1 1
    .ds 2 2
    .ds 3 3
    .ds 4 4
    .ds 5 5
    .ds 6 6
    .ds 7 7
    .ds 8 8
    .ds 9 9
    .ds 10 A
    .ds 11 B
    .ds 12 C
    .ds 13 D
    .ds 14 E
    .ds 15 F
    .
    .nr n 0 1
    .while (\n[n] < 16) \{\
    \[u216\*[\nn]]
    .nr n +1
    .\}
    .br
    .
    .de m
    .nr n 0 1
    .while (\\n[n] < 16) \\{\\
    \\[u216\\*[\\nn]]
    .nr n +1
    .\\}
    ..
    .m
    $ troff -Tutf8 oliver.tr | grotty
    Ⅰ Ⅱ Ⅲ Ⅳ Ⅴ Ⅵ Ⅶ Ⅷ Ⅸ Ⅹ Ⅺ Ⅻ Ⅼ Ⅽ Ⅾ Ⅿ
    Ⅰ Ⅱ Ⅲ Ⅳ Ⅴ Ⅵ Ⅶ Ⅷ Ⅸ Ⅹ Ⅺ Ⅻ Ⅼ Ⅽ Ⅾ Ⅿ
    $

-- 
Cheers, Ralph.