# 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 ... An)←R
• Modify Assignment: Af←R
• Modify Strand Assignment: (A1 A2 ... An)f←R
• Hyperators: ∇ Z←L (LO (LH dhdo RH) RO) R
• Function/Operator/Hyperator Assignment: A←f,      A←op1,      A←op2
• Binding Strength: How Variables, Functions, Operators, Hyperators and other syntactic elements combine
• Sink: ←R
• Point Notation:
• Base16b10FFFF is a shorthand for 16⊥1 0 15 15 15 15 and 10b45v is a shorthand for 10⊥4 5 31.
• Euler2x3 is a shorthand for 2e3 or 2×(*1)*3 where e is Euler's Number (2.718281828459045...).
• Pi2<_p/>3 is a shorthand for 2π3 or 2×(○1)*3 where π is Archimedes' constant (3.141592653589793...).
• Gamma2g3 is a shorthand for 2γ3 where γ is Euler-Mascheroni's Constant (0.5772156649015329...).
• Hypercomplex2i3, 2J3 (both equal to 2+3×√¯1), 2ad3 (Angle in Degrees), 2ar3 (Angle in Radians), or 2au3 (Angle in Unit Normalized) for a Complex number, 1i2j3k4 for a Quaternion number, and 1i2j3k4l5ij6jk7kl8 for an Octonion number.
• Rational2r3 is a shorthand for 2÷3 as a Multiple-Precision Integer/Rational number.
• Variable-Precision Floating2.3v is a shorthand for 2.3 as a Multiple-Precision Floating Point number.
• Ball Arithmetic2.3±1¯17 is a shorthand for a Ball whose Midpoint and Radius are 2.3 and 1¯17, respectively.
• 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).
• Anonymous Functions/Operators/Hyperators: multi-line grouping of one or more statements all enclosed in braces such as {(+⌿⍵)÷≢⍵}.

## Primitive functions

where L is the Left argument, R is the Right argument, and [X] is an optional Axis value.

## Primitive operators

 Name Symbol/Syntax Derived Function Valence Axis {L} f[X] R,   {L} (f op1[X]) R,   {L} (f op2[X] g) R ambivalent Combinatorial a‼ R monadic Commute L f⍨ R ←→ R f L dyadic Composition {L} f⍥g R ambivalent Compose {L} f∘g R,   (f∘b) R,   a∘g R ambivalent/monadic Convolution L f⍡g R dyadic Determinant f.g R monadic Duplicate f⍨ R ←→ R f R monadic Matrix {L} f⌻ R,   ∘⌻ R ambivalent/monadic Multisets {L} f⍦ R ambivalent Null {L} f⊙ R ambivalent Power {L} f⍣g R,   {L} (f⍣b) R ambivalent Rank {L} (f⍤[X] b) R ambivalent Variant {L} (f⍠b) R ambivalent

where {L} is an optional Left argument, R is the Right argument, f and g represent Functions, a and b represent Variables, and [X] is an optional Axis value.

## 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