{optional-arguments} concerns commands and environments that accept optional arguments. For example the \sqrt command can be used as \sqrt[3]{x}.

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How to pass an optional argument to an environment with verbatim content?

This is an attempt to make clear what happened in this question of xport (now deleted, sorry). The now deleted question included code that tried to make my answer to this question of xport work for ...
22
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2answers
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Escaping square braces

I want to use some text as the optional parameter to some command. The text includes square braces ([ and ]), but since the optional parameter goes within square brackets, unexpected things happen. ...
17
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2answers
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Why do some commands use []s, some use {}s, and some use both?

I find it confusing to remember which commands take {} arguments, and which ones take [] arguments. Is there a rule-of-thumb or semantic difference between these two? If so, what? (Because they seem ...
5
votes
1answer
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Can BibTeX ignore optional arguments?

Is it possible to get BibTeX to ignore certain optional arguments? For example, if the .bib file has many entries with language = {English}, and you wish for a certain file's bibliography to not say ...
27
votes
5answers
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How can I use one argument as the default value for another?

I'd like to define a command that takes 1, 2 or 3 arguments, and where the 2nd gets the same value as the 1st if it is not defined. I tried \newcommand\codefrom[3][#1][Matlab]{ ... } but I get an ...
2
votes
1answer
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\newcommand that restricts the value of an argument

When defining a macro, is it possible to restrict the value of an argument, so that if the thing followed it is a number, then it takes it as an argument, but if it is not, then it is just empty. To ...
63
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5answers
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Different command definitions with and without optional argument

I want to define a command that expands to two completely different things depending on whether I supply, or not, an optional argument. For example, \mycmd{normal} -> something(normal) ...
13
votes
2answers
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How can one put a “[” after \item?

The following does not compile because of the "[" after the \item. I presume it is because LaTeX expects a "]" as per the \item[option] syntax. However, I just want to insert the "[" character into ...