Is there `map_apply` anywhere in the standard library?

No, there is no such thing.

The three-argument form of apply makes this cleaner, if the function you’re calling is public:

Enum.map(some_list, &apply(Kernel, :-, &1))

IMO even if a map_apply existed, it would still be clearer to use Enum.map(fn [a,b] -> a-b end) than any apply form.

For instance, the explicit pattern-match gives a better error message when passed malformed data:

iex(7)> a = [[2, 1], [4, 1], [1, 2, 3]]    
[[2, 1], [4, 1], [1, 2, 3]]

iex(8)> Enum.map(a, &apply(Kernel, :-, &1))
** (UndefinedFunctionError) function Kernel.-/3 is undefined or private. Did you mean:

      * -/1
      * -/2

    (elixir 1.13.4) Kernel.-(1, 2, 3)
    (elixir 1.13.4) lib/enum.ex:1593: Enum."-map/2-lists^map/1-0-"/2
    (elixir 1.13.4) lib/enum.ex:1593: Enum."-map/2-lists^map/1-0-"/2

iex(8)> Enum.map(a, fn [a, b] -> b - a end)
** (FunctionClauseError) no function clause matching in :erl_eval."-inside-an-interpreted-fun-"/1    
    
    The following arguments were given to :erl_eval."-inside-an-interpreted-fun-"/1:
    
        # 1
        [1, 2, 3]
    
    (stdlib 3.15.2) :erl_eval."-inside-an-interpreted-fun-"/1
    (stdlib 3.15.2) erl_eval.erl:834: :erl_eval.eval_fun/6
    (elixir 1.13.4) lib/enum.ex:1593: Enum."-map/2-lists^map/1-0-"/2
    (elixir 1.13.4) lib/enum.ex:1593: Enum."-map/2-lists^map/1-0-"/2

Then again, you might want the behavior for single-element lists:

iex(8)> a = [[2, 1], [4, 1], [1]]          
[[2, 1], [4, 1], [1]]

iex(9)> Enum.map(a, &apply(Kernel, :-, &1))
[1, 3, -1]

iex(10)> Enum.map(a, fn [a, b] -> b - a end)
** (FunctionClauseError) no function clause matching in :erl_eval."-inside-an-interpreted-fun-"/1    
    
    The following arguments were given to :erl_eval."-inside-an-interpreted-fun-"/1:
    
        # 1
        [1]
    
    (stdlib 3.15.2) :erl_eval."-inside-an-interpreted-fun-"/1
    (stdlib 3.15.2) erl_eval.erl:834: :erl_eval.eval_fun/6
    (elixir 1.13.4) lib/enum.ex:1593: Enum."-map/2-lists^map/1-0-"/2
    (elixir 1.13.4) lib/enum.ex:1593: Enum."-map/2-lists^map/1-0-"/2

Here the single-element list has called Kernel.-/1. Note that the nested-captures version (if it compiled) wouldn’t have this property, since it captures a single arity.

thx!

and duh on me! should have seen and registered the /3 version!