[Tex/LaTex] Optional parameter in newcommand

macrosoptional arguments

I have made a command

\newcommand{\mysec}[2]{%
 \textbf{#1} \\ #2
}

I use it with \mysec{A}{B}.

But sometimes I also want a third parameter. I could make a whole new command for those situations where I need 3 parameters. But I thought if I could handle it with an optional parameter in my original command?

So I have to check if the third parameter is set and how to print if it is set.

Best Answer

Optional parameters are in [] not {} and if using \newcommand always come first.

\newcommand{\mysec}[3][]{%
 \textbf{#2} \\ #3 #1%
}

allows

\mysec{aaa}{bbb}

\mysec[ccc]{aaa}{bbb}

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[Tex/LaTex] Optional Parameters in xparse: \IfBooleanTF vs \IfNoValueTF

Yes, the above is correct.

The two cases are logically distinct as you are passing different information. The aim of xparse is to make this structural information clear.

For \IfBoolean(TF), the argument is a single token which can only be one of two values: TRUE and FALSE. A value is always returned by the t (and s) argument types, and the test is there to see which it is. One may also reverse the logic returned here using \ReverseBoolean: the presence of the token does not have to map to logically TRUE.

\DeclareDocumentCommand \foo { >{ \ReverseBoolean } s }
   {
      \IfBooleanTF #1
        { Star not present }
        { Star present }
   }

On the other hand, argument types which grab 'some tokens' may not be present (so yield \NoValue), be present-but-empty or be present-and-non-empty. The logic that something is present cannot be reversed so \IfNoValue will always be true only if the optional argument was not given at all.

The k-type argument has recently been adjusted: you now want e-type. This one is somewhat specialised and the team have had quite a bit of discussion about the correct form here.

Best Answer

Related Solutions

[Tex/LaTex] Optional Parameters in xparse: \IfBooleanTF vs \IfNoValueTF

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