Uiua

Uiua
Developer	Kai Schmidt
Released	2023
Latest release	2024 (unversioned)
Array model	flat with box-like niladic functions
Index origin	0
Function styles	stack-based tacit
Numeric types	64-bit float
Unicode support	full
File extensions	.ua
Implementation languages	Rust
Source code	GitHub
Platforms	native, in-browser
License	MIT
Website	uiua.org
Documentation	Documentation
Run online	Pad
Influenced by	Forth, BQN

Uiua is a stack-based array language designed by Kai Schmidt using glyphs inspired mainly by BQN.

Overview

Uiua uses concatenative evaluation (a context-free grammar) with a right-to-left ordering as in Polish notation. The language supports tacit programming using stack manipulation primitives, and all complex functions must be defined this way as there is no explicit function form that allows local variables. Functions have a fixed number of input and output values, meaning the overloading of ambivalent functions is removed. Because of this, Uiua often splits APL primitives into two functions. Its primitives use Unicode glyphs including many not found in other languages. To avoid the need for a keyboard layout containing these, each primitive can also be spelled using a name that consists of lowercase letters (user-defined names must have at least one uppercase letter). By default, the language formats source files when run to convert these names into the corresponding glyphs.

Like the SHARP APL family, arrays are flat with a homogeneous type; however, functions in Uiua are first-class values, and instead of boxes, niladic constant-valued functions are used to provide array nesting.

Uiua was featured on Array Cast in 2023.

Primitives

Function

Stack

Work with the stack

Table of Stack function in Uiua

Glyph	Name	Type	Definition
.	Duplicate	Monadic 2-output function	Duplicate the top value on the stack
,	Over	Dyadic 3-output function	Duplicate the second-to-top value to the top of the stack
:	Flip	Dyadic 2-output function	Swap the top two values on the stack
◌(;)	Pop	Monadic 0-output function	Discard the top stack value
?	Stack	Noadic 0-output function	Debug print all stack values without popping them
⸮	Trace	Monadic function	Debug print the top value on the stack without popping it

Constants

Push a constant value onto the stack

Table of Constants in Uiua

Glyph	Name	Definition
η	Eta	The number of radians in a quarter circle
π	Pi	The ratio of a circle's circumference to its diameter
τ	Tau	The ratio of a circle's circumference to its radius
∞	Infinity	The biggest number

Monadic Pervasive

Operate on every element in an array

Table of Monadic Pervasive in Uiua

Glyph	Name	Definition
¬	Not	Logical not
±	Sign	Numerical sign (1, ¯1, or 0)

External links

• Uiua on the concatenative language wiki