What do you think about "functional selective specification"? I just added this to iv:
A←3 3⍴⍳9 ⋄ A[{⍺[2]>⍺[1]}]←0 ⋄ A
A←10×3 3⍴⍳9 ⋄ A[{(⍵>30)^⍵<60}]←0 ⋄ A
The function is given in the index specification (brackets). It receives the index vector on the left and the scalar value on the right for each element. If it returns 1, it selects, for 0 or empty it does not.
The difference to other methods is, that it may decide on the indexes as well as on the value.
A←3 3⍴⍳9 ⋄ A[{⍺[2]>⍺[1]}]←0 ⋄ A
A←10×3 3⍴⍳9 ⋄ A[{(⍵>30)^⍵<60}]←0 ⋄ A
The function is given in the index specification (brackets). It receives the index vector on the left and the scalar value on the right for each element. If it returns 1, it selects, for 0 or empty it does not.
The difference to other methods is, that it may decide on the indexes as well as on the value.