Simple examples

This page will contain examples that serve well to show APL's strength. They require minimal background and have no special dependencies.

Text processing

APL represents text as character lists (vectors), making many text operations trivial.

Indices of multiple elements

∊ gives us a mask for elements (characters) in the left argument that are members of the right argument:

      'mississippi'∊'sp'
0 0 1 1 0 1 1 0 1 1 0

⍸ gives us the indices where true (1):

      ⍸'mississippi'∊'sp'
3 4 6 7 9 10

We can combine this into an anonymous infix (dyadic) function:

      'mississippi' (⍸∊) 'sp'
3 4 6 7 9 10

Parenthesis nesting level

      +\-⌿'()'∘.='plus(square(a),plus(square(b),times(2,plus(a,b)))'
0 0 0 0 1 1 1 1 1 1 1 2 2 1 1 1 1 1 1 2 2 2 2 2 2 2 3 3 2 2 2 2 2 2 2 3 3 3 3 3 3 3 4 4 4 4 3 2 1