Modify Strand Assignment

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(A1 A2 ... An)f←R In general, assigns Ai←Aif i⊃R.
A1 A2 ... An are all names with existing values, f is an arbitrary dyadic function, and R is a scalar or vector.
If 1<⍴⍴R, signal a RANK ERROR.
If R is a scalar or one element vector, its item, in combination with the value of each name, is assigned to each name, as in Ai←Aif ⊃⍬⍴R.
Otherwise, assume there are n names in the list:
If n≠⍴R, signal a LENGTH ERROR.
Otherwise, each successive item of R, in combination with the value of each successive name, is assigned to each successive name, as in Ai←Aif i⊃R.


For example, (A B C)⍴←⊂⍳3 is shorthand for A←A⍴⍳3 ⋄ B←B⍴⍳3 ⋄ C←C⍴⍳3. In contrast, (A B C)⍴←⍳3 is shorthand for A←A⍴1 ⋄ B←B⍴2 ⋄ C←C⍴3.