MicrosoftIn this proposal, the LET function is being used to pass a function input using DEF (sometimes referred to as an anonymous function) and the MAP function then iterates over the value inputs (this is standard terminology in functional languages).
As an example of how this LET syntax could be used in practice, suppose you want to evaluate one of three UDFs: x(Range), y(Range) or z(Range) according to an input value i = 1, 2 or 3. Either of the following formulas will do the job:
=CHOOSE(i,x(Range),y(Range),z(Range)) =LET(f,CHOOSE(i,x,y,z),f(Range))
to be concrete one could define:
Function x(range)
x = Application.Min(range)
End Function
Function y(range)
y = Application.Max(range)
End Function
Function z(range)
z = Application.Average(range)
End Function