APL syntax

APL's core syntactic principles are:

• Arrays as first class citizens
• Functions take arrays as argument(s) and produce arrays as result
• Functions have long right scope
• Operators take functions and/or arrays as operand(s) and produce derived functions
• Operators have long left scope

Example array definitions

      simplenumvec←1 2 3 4 ⍝ A simple numeric vector
      simplecharvec←'ABCD' ⍝ A simple character vector

Example function definition

    ∇  r←l Tradfn r              
[1]    ⍝ An infix (dyadic) tradfn
[2]    r←l r                     
    ∇  

Works in: Dyalog APL, APL2, GNU APL, NARS2000

Example operator definition

     ∇ r←larg(Main OVER PreProc)rarg                                                 
[1]    r←(PreProc larg)Main(PreProc rarg)                                            
     ∇  

Example function application

      ÷3         ⍝ Prefix primitive function
0.3333333333
      1+2        ⍝ Infix primitive function
3
      +/1 2 3 4  ⍝ Prefix primitive derived function
10
      2+/1 2 3 4 ⍝ Infix primitive derived function
3 5 7

Scoping rules