ṁ - Mold (Reshape)
This atom is dyadic, which means it takes two arguments.
Reshape the elements of
x into the structure of
Specifically, the elements of
x (automatically cast to a singleton list) are cycled through to fill the elements of
y in the order they would appear if
y were Flattened (
x is not flattened, however, so
[1,2],3 ṁ 1,2,[3,4] returns
[[1, 2], 3, [[1, 2], 3]].