ConTeXt: Comparing macro result to string

Question

This seems like a very basic question and I'm sure it's been answered somewhere, but I can't find anything on it. The closest I've gotten is this question, but neither of the solutions in the accepted answer help my code.

I'm trying to branch based on the value of a namespace parameter. If I replace the \namedordefaulteraparameter{#1}{formatdecoration} with a literal yes, I get "y" as I'd expect, and just printing the value of that macro also gives me the "yes" it should. However, when I pass the macro to the test, I always get "n". I'm guessing that this is due to \doifsamestringelse testing the values without expanding them, but no matter how many \expandafters I use or where I put them, I can't get the first result to be included. What am I missing?

\definenamespace[era][
    type=module,
    name=era,
    command=yes,
    setup=yes,
]

\setupera[
    formatdecoration=yes,
]

\define[2]\namedordefaulteraparameter{%
    \doifsomethingelse
        {\namederaparameter{#1}{#2}}
        {\namederaparameter{#1}{#2}}
        {\eraparameter{#2}}%
}

\def\eradecorated[#1]#2{%
    \doifsamestringelse{yes}{\namedordefaulteraparameter{#1}{formatdecoration}}
        {y}
        {n}%
}

I know I could do this pretty easily in Lua, but for something so simple, I don't see any reason to add that extra syntax.

Answer 1

There are several flaws in your example:

1. \doifsamestringelse will detokenize both strings and then comapare the result. You have to use \doifelse instead.
2. \namedordefaulteraparameter is not expandable, but for \doifelse to ever be true both operands must expand to the same result.
3. \doifsomethingelse is not expandable. You have to use the expandable alternative \expdoifelse.

Implementing an expandable test and making everything in between expandable as well, we are ready to go.

\definenamespace[era][
    type=module,
    name=era,
    command=yes,
    setup=yes,
]

\setupera[
    formatdecoration=yes,
]

\def\namedordefaulteraparameter#1#2{%
    \expdoifelse{\namederaparameter{#1}{#2}}{}%
        {\eraparameter{#2}}%
        {\namederaparameter{#1}{#2}}%
}

\def\eradecorated[#1]#2{%
    \expdoifelse{yes}{\namedordefaulteraparameter{#1}{formatdecoration}}%
        {y}%
        {n}%
}

\starttext

\eradecorated[era]{}

\stoptext

Answer 2

I am not sure why you are defining \namedordefaultparameter. The standard way to fall back on a default argument is as follows:

\definenamespace
  [era]
  [
    type=module,
    name=era,
    command=yes,
    setup=yes,
    parent=era, % NOTE: Added this!!
  ]

\setupera
  [
    formatdecoration=yes,
  ]

\defineera[test1][formatdecoration=no]
\defineera[test2]

\starttext

\namederaparameter{test1}{formatdecoration}
\namederaparameter{test2}{formatdecoration}


\stoptext

which gives

no yes

Based on this, you can define \eradecorated macro as follows:

\def\eradecorated[#1]%
    {\doifelse{\namederaparameter{#1}{formatdecoration}}{yes}
      {y}{n}}

and use it as

\eradecorated[test1]
\eradecorated[test2]

which gives

n y

Note that, strictly speaking, the above macro is not equivalent to the one that you defined. If I set \defineera[test2][formatdefinition=], then my macro gives the result n n, while you macro still gives the result n y. I don't know whether you care about the difference or not.