General ⇒ Defining / Redefining Variables

[eleanor]

Hi.

I would like to achieve something like this: I have defined a new command with \newcommand and I'm passing an argument to it, like this: pdf, text, doc - which is the filetype. So what I want to achieve is to define a variable like this:

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\def\filetype{text}

And then compare which extension was inputed like this:

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\ifthenelse{\equal{#1}{pdf}}{\let\filetype{pdf}}

The problem is that the latter redefinition of the filetype variable doesn't work. Does anybody have any idea how can I achieve this.

Thanks in advance

[Stefan Kottwitz]

Hi Eleanor,

you can use \newcommand do define a macro and \renewcommand to redefine the macro later. These are LaTeX macros, whereas \def and \let are TeX primitives.

Stefan

[cgnieder]

Although this is a rather old question I'd like to explain in a little more detail why

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\ifthenelse{\equal{#1}{pdf}}{\let\filetype{pdf}}

can't work:
The problem is \let\filetype{pdf}; \let can only define one token to be another one.

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\let<token1><token2>

or

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\let<token1>=<token2>

An example would be something like this:

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\def\foo{foo}%
\def\bar{bar}%
\let\foo\bar
\show\foo

gives (in the log):

> \foo=macro:
->bar.

In the case at hand one can use for instance \def instead:

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\documentclass{article}
\usepackage{ifthen}
\def\filetype{tex}
\newcommand*\setfiletype[1]{%
  \ifthenelse{\equal{#1}{pdf}}{\def\filetype{pdf}}{}}
\begin{document} 

\setfiletype{dvi}
\filetype

\setfiletype{pdf}
\filetype

\end{document}

This will give:

tex
pdf

Regards