Language Features

At the moment, the following sections describe only those language features that are New or Enhanced relative to the Extended APL Standard, or that deserve special comment.

Syntax

• Strand Assignment: (A₁ A₂ ... A_n)←R
• Modify Assignment: Af←R
• Modify Strand Assignment: (A₁ A₂ ... A_n)f←R
• Function/Operator Assignment: A←f,   A←op1,   A←op2
• Sink: ←R
• Point Notation:
  • Base — 16b10FFFF as a shorthand for 16⊥1 0 15 15 15 15
  • Pi — 2p3 as a shorthand for 2π³ or 2×(○1)*3
  • Euler — 2x3 as a shorthand for 2e³ or 2×(*1)*3.
• Trains: e.g., avg←(+/ ÷ >) applies the functions to its argument(s) in a particular way (in this case, to compute the average of a numeric vector).
• System Labels: ⎕PRO and ⎕ID in user-defined functions/operators.

Primitive functions

• Find: L⍷R
• Index Generator: ⍳R
• Index Of: L⍳R
• Indexing: R[L],   R[L]←A,   R[L]f←A,   L⌷R,   L⍉R,    L⊃R
• Indices: ⍸R
• Matrix Inverse/Divide: ⌹R,   L⌹R
• Mismatch: L≢R
• Partitioned Enclose: L⊂[X] R
• Primes: πR and LπR
• Reshape: L⍴R
• Root: √R and L√R
• Tally: >R
• Without: L~R

Primitive operators

• Axis: f[X], f op1[X], f op2[X]g
• Composition: f⍥g
• Compose: f∘g,   f∘R,   L∘g
• Multisets: f⍦
• Null: f⊙
• Rank: f⍤[X] Y

Datatypes

• Infinity: ∞ and ¯∞
• Arithmetic Progression Arrays: 2 3 4⍴⍳24
• Unicode Characters
• Array Predicates
• Rational: 1r3 and 1234rx
• Variable-precision Floating Point: 1v234 and 12v

System Functions

• ⎕A (Uppercase English Alphabet)
• ⎕AT (Object Attributes)
• ⎕AV (Atomic Vector)
• ⎕CR (Canonical Representation)
• ⎕DM (Diagnostic Message)
• ⎕DR (Data Representation)
• ⎕EA (Execute Alternate)
• ⎕EC (Execute Controlled)
• ⎕EM (Event Message)
• ⎕ERROR (Signal Error)
• ⎕ES (Event Simulate)
• ⎕ET (Event Type)
• ⎕FMT (Format)
• ⎕MF (Monitor Function)
• ⎕NC (Name Class)
• ⎕NL (Name List)
• ⎕SYSID (System Identifier)
• ⎕SYSVER (System Version)
• ⎕TC/⎕TCxxx (Terminal Control)
• ⎕TF (Transfer Form)
• ⎕UCS (Universal Character Set)
• ⎕VR (Visual Representation)
• ⎕WA (Workspace Available)

System Variables

• Scalar System Variables (⎕CT,   ⎕IO,   ⎕PP,   ⎕PW,   ⎕RL)
• ⎕ELX (Error Trapping)
• ⎕FC (Format Control)
• ⎕IC (Indeterminate Control)