I have an association
<| a->f, b->g |> where f and g are pure functions. Is there a nice way to apply arguments to both f and g? E.g.
<| a->f, b->g |>[x] --> <| a->f[x], b->g[x] |> $\begingroup$ $\endgroup$
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4 Answers
$\begingroup$ $\endgroup$
3 As Kuba provided in a comment we can Map a Function that applies its argument to a specific expression, e.g. x:
#[x] & /@ <|a -> f, b -> g|> <|a -> f[x], b -> g[x]|>
- $\begingroup$ Still, as did OP, I'd expect Through to work (does it?) $\endgroup$LLlAMnYP– LLlAMnYP2017-09-26 08:16:25 +00:00Commented Sep 26, 2017 at 8:16
- $\begingroup$ @LLlAMnYP you mean like
Through[<|a -> f, b -> g|>[x]]? No, it does not; the body evaluates toMissing["KeyAbsent", x].Through[Unevaluated[<|a -> f, b -> g|>[x]]]givesAssociation[(a -> f)[x], (b -> g)[x]]but I don't find that helpful.With[{asc = <|a -> f, b -> g|>}, Through[Unevaluated[asc[x]]]]just kicks backThrough[Unevaluated[<|a -> f, b -> g|>[x]]]. $\endgroup$Mr.Wizard– Mr.Wizard2017-09-26 08:37:07 +00:00Commented Sep 26, 2017 at 8:37 - $\begingroup$ Thanks, I do not mind a non cw answer next time :) $\endgroup$Kuba– Kuba2017-09-26 09:42:36 +00:00Commented Sep 26, 2017 at 9:42
$\begingroup$ $\endgroup$
Using Comap (new in 14.0)
Comap[<|a -> f, b -> g|>, x] <|a -> f[x], b -> g[x]|>
$\begingroup$ $\endgroup$
If your version of WL doesn't have Comap (version version 14), you could also use Query:
Query[<|a -> f, b -> g|>][x] <|a -> f[x], b -> g[x]|>
$\begingroup$ $\endgroup$
From @Gustavo Delfino's answer and Query[<|a -> f, b -> g|>] // Normal,
GeneralUtilities`ApplyThrough[<|a -> f, b -> g|>][x] (* <|a -> f[x], b -> g[x]|> *) (Community wiki)