\define a command with square-bracket arguments

\define a command with square-bracket arguments

[Sietse Brouwer]

Hi all,

As I understand it, \define[2] is preferred over \def#1#2 because it
refuses to overwrite existing commands.

\define[2]\mycommand{code code code}
defines a command to be invoked with
\mycommand{...}{...}

Can I use \define, or a related command, to define a command that
takes square-bracket arguments, like so:
\mycommand[...][...]
?

When I type
\define[1][2]\mycommand{code code code}
that doesn't work.

Cheers,
Sietse
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Re: \define a command with square-bracket arguments

[Thomas A. Schmitz]

On 09/27/2012 05:45 PM, Sietse Brouwer wrote:
> Hi all,
>
> As I understand it, \define[2] is preferred over \def#1#2 because it
> refuses to overwrite existing commands.
>
> \define[2]\mycommand{code code code}
> defines a command to be invoked with
> \mycommand{...}{...}
>
> Can I use \define, or a related command, to define a command that
> takes square-bracket arguments, like so:
> \mycommand[...][...]
> ?
>
> When I type
> \define[1][2]\mycommand{code code code}
> that doesn't work.
>
> Cheers,
> Sietse
> _______

You know the wiki better than most, but I wonder: are you looking for 
this page?

http://wiki.contextgarden.net/Commands_with_optional_arguments

Thomas
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Re: \define a command with square-bracket arguments

[Marco Patzer]

2012-09-27 Sietse Brouwer <sbbrouwer@gmail.com>:

Hi Sietse,

> As I understand it, \define[2] is preferred over \def#1#2 because it
> refuses to overwrite existing commands.

\define overwrites existing commands with pleasure. In contrast to
\def it prints a message to the log file: “\mycommand is already
defined”.

> Can I use \define, or a related command, to define a command that
> takes square-bracket arguments, like so:
> \mycommand[...][...]

\def\mycommand
  {\dodoubleempty\domycommand}

\def\domycommand [#1][#2]
  {first: #1, second: #2}

\mycommand [foo] [bar]
\mycommand [foo][bar]
\mycommand [foo]

Question for the others: What's the difference of \dodoubleargument
and \dodoubleempty? I expected \dodoubleargument to throw an error
since the arguments are supposed to be mandatory.


Marco

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Re: \define a command with square-bracket arguments

[Sietse Brouwer]

Hi Marco,

> \define overwrites existing commands with pleasure. In contrast to
> \def it prints a message to the log file: “\mycommand is already
> defined”.

Ah, then I am not particularly bothered about using \def instead of
\define for my square-bracket-taking commands. Thanks!

Thomas wrote:
> are you looking for this page?
> http://wiki.contextgarden.net/Commands_with_optional_arguments

I wasn't looking for that page, but on that note: I've found out where
the Lua argument-to-table parsers reside! This makes me very happy.
More in a separate e-mail, to follow.

Cheers,
Sietse
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Re: \define a command with square-bracket arguments

[Wolfgang Schuster]

Am 27.09.2012 um 18:16 schrieb Marco Patzer <homerow@lavabit.com>:

> Question for the others: What's the difference of \dodoubleargument
> and \dodoubleempty? I expected \dodoubleargument to throw an error
> since the arguments are supposed to be mandatory.

In MkIV Hans didn’t add this check and in MkII he disabled is for command
with three or less argument but even then you get only a message in the log
when your command has no argument (i.e. a command with four argument
complains only when it has zero argument but doesn’t complain when it
has one to four arguments).

Even though there is no difference between the \*empty and \*argument
commands I would use both because you can see in the source that
a command with \*argument has mandatory arguments while the
argument for a \*empty command are optional.

Wolfgang
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Re: \define a command with square-bracket arguments

[Sietse Brouwer]

>> Question for the others: What's the difference of \dodoubleargument
>> and \dodoubleempty? I expected \dodoubleargument to throw an error
>> since the arguments are supposed to be mandatory.
>
> In MkIV Hans didn’t add this check and in MkII he disabled is for command
> with three or less argument but even then you get only a message in the log
> when your command has no argument (i.e. a command with four argument
> complains only when it has zero argument but doesn’t complain when it
> has one to four arguments).

Wikified: http://wiki.contextgarden.net/Command/dodoubleempty
(I've been meaning to document that command for a while now. As a
complement to the existing explanation at
http://wiki.contextgarden.net/Commands_with_optional_arguments, I mean.)

--Sietse
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Re: \define a command with square-bracket arguments

[Hans Hagen]

On 28-9-2012 14:41, Sietse Brouwer wrote:
>>> Question for the others: What's the difference of \dodoubleargument
>>> and \dodoubleempty? I expected \dodoubleargument to throw an error
>>> since the arguments are supposed to be mandatory.
>>
>> In MkIV Hans didn’t add this check and in MkII he disabled is for command
>> with three or less argument but even then you get only a message in the log
>> when your command has no argument (i.e. a command with four argument
>> complains only when it has zero argument but doesn’t complain when it
>> has one to four arguments).
>
> Wikified: http://wiki.contextgarden.net/Command/dodoubleempty
> (I've been meaning to document that command for a while now. As a
> complement to the existing explanation at
> http://wiki.contextgarden.net/Commands_with_optional_arguments, I mean.)

Originally the 'argument' variant reported a message but when the code 
was cleaned up that went away ... actually it means that we can say:

\let\dosingleargument    \dosingleempty
\let\dodoubleargument    \dodoubleempty
\let\dotripleargument    \dotripleempty
\let\doquadrupleargument \doquadrupleempty
\let\doquintupleargument \doquintupleempty
\let\dosixtupleargument  \dosixtupleempty
\let\doseventupleargument\doseventupleempty

in syst-aux.mkiv, which is somewhat more efficient

There is still checking in the {} variants.

Hans


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