Is it possible to use apply() with a rule/function where the array is not the fi

forum.appian.com/.../Expressions

Shows how parameters can be passed by keyword, but it's not clear to me how I would do this for a looping function.

I'm also seeing some unusual syntax that I can't find documented on the looping functions page here: forum.appian.com/.../Function_Recipes

apply(
type!Person(firstName:_, lastName:_),
merge(pv!firstNames, pv!lastNames)
)

How do I use apply with a rule, type, or function and include the parameters by keyword? I cannot find documentation explaining how the underscores are being used here as blanks, either.

One option is to create an expression rule that switches the inputs of the function so that the array is the first argument and can be applied over.

Here is some documentation on partial evaluations (underscore syntax):
forum.appian.com/.../Expressions

Thanks for the partial evaluation link. I've used the rule to switch input order work-around before, but I was wondering if there was a more elegant method.

The more elegant method is to use partial functions. For example, if you want to apply over the index function, but you want to apply over the second parameter, not the first, you can do the following:

apply(fn!index(firstArray,_,default),secondArray)

An expression like this should apply over the second array.

That is a very nice trick, Steven. Any chance that could be added to the looping functions documentation page as an example?