Xtykutl

Suppose you want to define page style depending on a boolean value.

I think both constructions below have equivalent output (or not?), but which is better/more indicated/professional/elegant?

if@mybool

    defps@myps{

        % definition here

    }

else

    defps@myps{

        % definition here

    }

fi

or

defps@myps{

    if@mybool

        % definition here

    else

        % definition here

    fi

}

The two constructs aren't equivalent.

With

if@mybool

  defps@myps{...T...}%

else

  defps@myps{...F...}%

fi

you test if@mybool and define ps@myps according to its truth value. Changing the value later in the document will not change the definition of ps@myps.

To the contrary,

defps@myps{%

  if@mybool

    ...A...%

  else

    ...B...%

  fi

}

will yield ...A... or ...B... according the the truth value of if@mybool at the time the macro is expanded.

Which one to use depends on what you need to achieve.

With the first definition, if issued when if@mybool is true,

@myboolfalse

ps@myps

@myboolfalse

ps@myps

will produce ...A... twice.

With the second definition, the above code would produce first ...B... and then ...A....

If you are writing a package and if@mybool is set by a package options at runtime, most likely you want to use the first model, as the macro name suggests you're trying to define a page style that probably shouldn't change mid document.

The situation is quite similar to let and def. With letmymacroanother you define mymacro to be the same another is at the time the let instruction is performed.

With defmymacro{another}, the meaning of another current at the moment mymacro is called will be used, which can have changed in the meantime.