Assignment

You can assign a value to a variable with the glyph: '←'.

Common examples (boxing on, and ⎕io is 0):

   mat←(1 2 3)(1 2 3)
   mat

┌─────┬─────┐ │1 2 3│1 2 3│ └─────┴─────┘

   mat[0]←1  ⍝ indexed assignment
   mat

┌─┬─────┐ │1│1 2 3│ └─┴─────┘

   mat←3 3⍴⍳9
   mat

0 1 2 3 4 5 6 7 8

   mat[0 1;]  ⍝ 1 semicolon is necessary when dealing with 2D arrays, 2 semicolons for 3D arrays etc.

0 1 2 3 4 5

   mat[0 1;0 1]←0
   mat

0 0 2 0 0 5 6 7 8

   ⍝ incrementing (or any dyadic function) parts of an array
   mat←3 3⍴0
   mat

0 0 0 0 0 0 0 0 0

   mat[0 1;1]+←1
   mat

0 1 0 0 1 0 0 0 0

   mat[1;1],←'x'
   mat

0 1 0 0 x 0 0 0 0