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.
• Gamma — 2g3 as a shorthand for 2γ³ where γ is the Euler-Mascheroni Constant.

• 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 scalar or vector).
• System Labels: ⎕ID, ⎕MS, and ⎕PRO in user-defined functions/operators.
• Anonymous Functions/Operators: one-line grouping of one or more statements all enclosed in braces such as {(+⌿⍵)÷≢⍵}.

Primitive functions

• Array Lookup: L⍸R
• 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
• Sequence: L..R
• Sets: L§R, L⊆R, 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
• Convolution: f⍡g     (dyadic derived function)
• Determinant: f.g     (monadic derived function)
• Multisets: f⍦
• Null: f⊙
• Rank: f⍤[X] Y
• Variant: f⍠V

Datatypes

• Infinity: ∞ and ¯∞
• Arithmetic Progression Arrays: 2 3 4⍴⍳24
• Unicode Characters
• Array Predicates
• Rational Numbers: 1r3 and 12345x
• Variable-precision Floating Point (VFP) Numbers: 1.234v and 12v

System Commands

System Commands provide features to the user of the APL system, separate from actual workspaces, variables or APL operators. These provide such features as accessing files, saving a workspace, and exiting the APL interpreter. The commands are not case sensitive, so )IN and )in do the same thing.

NARS2000 currently has the following system commands:

)BOX Turn ON/OFF box around output )CLEAR Start a new session manager window with an empty workspace )CLOSE )COPY )DROP )EDIT Create a new function in the workspace or edit an existing function )ERASE Delete a variable or function in the current workspace )EXIT Close down the interpreter and exit the program. Same as )OFF )FNS )FOP Display functions, operators, and hyperators. Same as )FOPS )FOPS )HYP Display hyperators only )IN )INASCII     )LIB )LAOD Alternative spelling of )LOAD )LOAD Load an existing workspace )NEWTAB

)NMS )OFF Close down the interpreter and exit the program. Same as )EXIT )OPEN )OPS Display operators only )OUT )RESET )SAVE Save the current workspace )SVAE Alternative spelling for )SAVE )SI workspace State Indicator )SIC State Indicator Clear )SINL )SYMB )ULIB )VARS )XLOAD )WSID

System Variables and Functions

System Variables (A value may be assigned to these except for ⎕DM)
⎕ALX	⎕CT	⎕DM	⎕DT	⎕ELX	⎕FC	⎕FEATURE	⎕FPC	⎕IC	⎕IO
⎕LR	⎕LX	⎕PP	⎕PR	⎕PW	⎕RL	⎕SA	⎕WSID
Niladic System Functions (a value cannot be assigned to these)
⎕A	⎕AV	⎕EM	⎕ET	⎕LC	⎕NNAMES	⎕NNUMS	⎕SI	⎕SYSID	⎕SYSVER
⎕T	⎕TC	⎕TCBEL	⎕TCBS	⎕TCESC	⎕TCFF	⎕TCHT	⎕TCLF	⎕TCNL	⎕TCNUL
⎕TS	⎕WA
Monadic or dyadic system functions (a value cannot be assigned to these)
⎕AT	⎕CR	⎕DC	⎕DFT	⎕DL	⎕DR	⎕EA	⎕EC	⎕ERROR	⎕ES
⎕EX	⎕FMT	⎕FX	⎕MF	⎕NAPPEND	⎕NC	⎕NCREATE	⎕NERASE	⎕NINFO	⎕NL
⎕NLOCK	⎕NREAD	⎕NRENAME	⎕NREPLACE	⎕NRESIZE	⎕NSIZE	⎕NTIE	⎕NUNTIE	⎕STOP	⎕TF
⎕TRACE	⎕UCS	⎕VR
Note that quad functions and variables (except for the ⎕A family of functions) are case insensitive