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