⍴ Reshape r←x⍴y

x must be a vector of integers. Either all elements are natural, or exactly one of them is ¯1 and all others are natural.

r is the elements of y reshaped to the shape defined by x:

• if ×/x is equal to ×/⍴y, the elements of y are simply reordered to fit the new shape x
• if ×/x is positive and less than ×/⍴y, elements of y are dropped from the end to fit the new shape
• if ×/x is greater than ×/⍴y, elements of y are repeated cyclically to fit the new shape
• if ¯1∊x, the product of all elements of x that are not ¯1 must be a divisor of the amount of elements of y, and the resulting shape is obtained by substituting (×/⍴y)÷×/x⌿⍨¯1≠x for the ¯1 in x.

Fails if y is empty and x describes a nonempty shape.