Command to trap mutually exclusive program options

[Joseph Coveney]

There is a Stata programming command or function that traps a user's specifying more than one of a set of mutually exclusive, collectively exhaustive options.

I believe that it used to be in the list of undocumented commands and functions, but I cannot find it anymore anywhere (help files & user manual entries for syntax, programming; Googling related phrases).

Can someone point me to it?

Typical use case would be like the following:

program myprogram
    syntax . . . ., [Up Down]

    _whatI'mlookingfor(up down)

If a user accidentally entered

myprogram . . ., up down

it would return an error to the effect that "only one of up down may be specified".

[Maarten Buis]

help opts_exclusive

[Joseph Coveney]

Yeah, thank you for this. Found it just a moment ago on my own. It's still "undocumented".

[Maarten Buis]

It is one of those commands that I know exists, but somehow I always forget when I need it...

[Joseph Coveney]

It is one of those commands that I know exists, but somehow I always forget when I need it...

Yep, that's what happened to me, too. Thanks again, Maarten. I appreciate your rapid reply very much.

[Bjarte Aagnes]

add example of use from collect.ado version 1.0.3

program ParseWarn
    syntax name(name=c_cmd) [, NOWARN WARN]

    opts_exclusive "`nowarn' `warn'"
    if "`nowarn'" != "" {
        local set set collect_warn off
    }
    else if "`warn'" != "" {
        local set set collect_warn on
    }
    c_local `c_cmd' `set'
end