Need to understand the principle of the distinction between f[x_,y_] and f[x_][y_]
It seems also that
z[x_, y_][a_, b_, c_][α_, β_] := a (x + y)^b + c/(α-β)
is interpreted by Mathematica since
Plot3D[z[x, y][2, 5, 3][2, 4], {x, 0, 1}, {y, 0, 1}]
gives a nice plot. It could be useful to distinguish between variables and two types of parameters. But, in that case, how to use association like
data1 = Association[Thread[{"a", "b", "c"} -> {.5, 1, 1}]]
data2 = Association[Thread[{"α", "β"} -> {.2, 3}]]
--- how to use Apply --- @@ ---
NB David Park shows to me that how to do in the simple following case
b[x_][y_] := x^y
da = Association[Thread[{"x"} -> {.5}]]
(b @@ Values[da])[y]
If the association is on the first bracket-couple I can reproduce the example, but I do not know how to do it for a second bracket association.