APL syntax

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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

      simplenumvec1 2 3 4 ⍝ A simple numeric vector
      simplecharvec'ABCD' ⍝ A simple character vector

Example function definition

      rl Tradfn r              
[1]    ⍝ An infix (dyadic) tradfn
[2]    rl r                     
    

Example operator definition

      rlarg(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

Functions

Operators

APL dialects [edit]
Maintained APL+Win (APL*PLUS) ∙ APL2APL64APL\ivCo-dfnsDyalog APLdzaima/APLGNU APLNARS2000ngn/apl
Historical Iverson notationA Programming LanguageA+ (A) ∙ APL#APL.68000APL.SVAPLXAPL\1130APL\360NARSopenAPLRowanSHARP APL (SAX) ∙ VisualAPL (APLNext) ∙ VSAPLYork APL
Derivatives ELIJK (Q, KDB+) ∙ LYaPASNialRAD