elmar@expbinfo.uni-paderborn.de (Elmar Schalueck) (01/24/91)
% I discovered a beautiful difference in macros depending
% on the position of the left braces after the macroname.
% Is this a desired effect and how can I make use of it to apply
% macros to whole words that are not surrounded by braces?
%
% Greetings and have some fun with the example below
%
% Elmar Schal\"{u}ck elmar@uni-paderborn.de
%
%
\documentstyle{article}
\begin{document}
\long\def\foo#1
{Hurrah #1 Hurrah}
\long\def\gnat#1{Yippee #1 Yippee}
Now I test \foo{Why} and \gnat{Why not?} and everything's ok.
But watch out for the difference to \foo{Me}-too and \gnat{You}-never.
\end{document}jeburke@jhunix.HCF.JHU.EDU (John Burke) (01/24/91)
In article <1991Jan24.095405.8868@uni-paderborn.de> elmar@pbinfo.UUCP (Elmar Schalueck) writes: >% I discovered a beautiful difference in macros depending >% on the position of the left braces after the macroname. >% Is this a desired effect and how can I make use of it to apply >% macros to whole words that are not surrounded by braces? >% >% Greetings and have some fun with the example below >% >% Elmar Schal\"{u}ck elmar@uni-paderborn.de >% >% >\documentstyle{article} >\begin{document} >\long\def\foo#1 >{Hurrah #1 Hurrah} >\long\def\gnat#1{Yippee #1 Yippee} >Now I test \foo{Why} and \gnat{Why not?} and everything's ok. > >But watch out for the difference to \foo{Me}-too and \gnat{You}-never. >\end{document} From _The TeXbook_, p. 201 (of my copy, anyway, pre-3.0): <dangerous bend> Caution: When you define a macro with simple parameters, as in these examples, you must be careful not to put blank spaces before the '{' that begins the replacement text. For example, '\def\row #1 #2 {...}' will not give the same result as '\def\row#1#2{...}', becuase the spaces after #1 and #2 tell TeX to look for arguments that are followed by spaces. (Arguments can be "delimited" in a fairly general way, as explained below.) But the space after \row is optional, as usual, becuase TeX always disregards spaces after control words. After you have said '\def\row#1#2{...}', you are allowed to put spaces between the arguments (e.g., '\row x n'), because TeX doesn't use single spaces as undelimited arguments. --- ... in other words, look for answers to all life's trying questions in the Good Book. Blessed be Donald Knuth, and the horse He rode in on. John Burke ---------- jeburke@jhunix.hcf.jhu.edu | Johns Hopkins doesn't Homewood Academic Computing Information Center| want my opinions. Why was The Johns Hokins University | he selling whiskey, though. ---------
ogawa@orion.arc.nasa.gov (Arthur Ogawa) (01/25/91)
The macro \foo, defined as
\long\def\foo#1
{Hurrah #1 Hurrah}
Has a delimited argument: the delimiter is the whitespace immediately
preceeding the left brace. In your document,
Now I test \foo{Why} and \gnat{Why not?} and everything's ok.
But watch out for the difference to \foo{Me}-too and \gnat{You}-never.
Your first instance traces to:
\foo #1 ->Hurrah #1 Hurrah
#1<-Why
In the second, it traces to
\foo #1 ->Hurrah #1 Hurrah
#1<-{Me}-too
This behaviour is easy to understand if you keep in mind that the argument to
\foo ends at the first whitespace character---unlike the definition of \gnat.
This is an attribute of TeX (see chapter 20 of the TeXbook), not a peculiarity
of LaTeX. Keep at it, your experimentation will pay off richly in a deeper
understanding of TeX!