Hy (programming language)

Hy
	Hy logo – Cuddles the cuttlefish
Paradigm	Multi-paradigm: procedural, functional, object-oriented, meta, reflective, generic
Family	Lisp
Designed by	Paul Tagliamonte
Developers	Core team
First appeared	2013; 11 years ago
Stable release	1.0.0 / 22 September 2024; 59 days ago
Scope	lexical, optionally dynamic[citation needed]
Platform	IA-32, x86-64
OS	Cross-platform
License	MIT-style
Filename extensions	.hy
Website	hylang.org
Influenced by
	Kawa, Clojure, Common Lisp

Hy is a dialect of the Lisp programming language designed to interact with Python by translating s-expressions into Python's abstract syntax tree (AST).^[2]^[3] Hy was introduced at Python Conference (PyCon) 2013 by Paul Tagliamonte.^[4] Lisp allows operating on code as data (metaprogramming), thus Hy can be used to write domain-specific languages.^[5]

Similar to Kawa's and Clojure's mappings onto the Java virtual machine (JVM),^[6]^[7] Hy is meant to operate as a transparent Lisp front-end for Python.^[8] It allows Python libraries, including the standard library, to be imported and accessed alongside Hy code with a compiling^{[note 1]} step where both languages are converted into Python's AST.^{[note 2]}^[9]^[10]^[11]

Example code

From the language documentation:^[12]

=> (print "Hy!")
Hy!
=> (defn salutationsnm [name] (print (+ "Hy " name "!")))
=> (salutationsnm "YourName")
Hy YourName!

^ The term "compiled" may apply to expressing Hy code in Python's AST or converting that AST into bytecode, the latter being dependent on the specific Python interpreter used and not Hy.
^ Hy is tested on Python 2.7, 3.4 through 3.6, and PyPy.

^ "Hy 1.0.0, the Lisp dialect for Python, has been released · hylang hy · Discussion #2608". Retrieved 23 September 2024.
^ Jaworski, Michał; Ziadé, Tarek (2019). Expert Python programming (Third ed.). Birmingham, U.K.: Packt Publishing. p. 173. ISBN 978-1-78980-677-9. OCLC 1125343555.
^ Danjou, Julien (2018). Serious Python: black-belt advice on deployment, scalability, testing, and more. San Francisco, CA: No Starch Press. pp. 145–149. ISBN 9781593278793. OCLC 1057729260.
^ Tagliamonte, Paul (2 April 2013). PyCon lightning talk (Speech). Python Conference (PyCon). Santa Clara. Retrieved 2 September 2014.
^ Tagliamonte, Paul (11 April 2014). Getting Hy on Python: How to implement a Lisp front-end to Python (Speech). PyCon. Montreal. Retrieved 2 September 2014.
^ Turto, Tuukka (14 February 2014). "Programming Can Be Fun with Hy". Open Source For You. Retrieved 2 September 2014.
^ Watson, Mark (2020). A Lisp Programmer Living in Python-Land: The Hy Programming Language (PDF). LeanBooks.
^ Edge, Jake (30 April 2014). "Getting Hy on Python". LWN.net. Retrieved 2 September 2014.
^ "Hy Documentation". hylang.org. Retrieved 3 September 2014.
^ Danjou, Julien (26 March 2014). "The AST". The Hacker's Guide to Python. pp. 165–172.
^ Kitchin, John (31 March 2016). "More on Hy and why I think it is a big deal". The Kitchin Research Group. Carnegie Mellon University. Retrieved 19 September 2018.
^ "Quickstart". Hylang.org. 15 May 2018. Retrieved 19 September 2018.

Timeline of Lisp dialects
v
t
e
1958	1965	1970	1975	1980	1985	1990	1995	2000	2005	2010	2020
LISP 1, 1.5, LISP 2^(abandoned)
	Maclisp
		Interlisp
		MDL
			Lisp Machine Lisp
			Scheme				R5RS		R6RS	R7RS small
			NIL
				ZIL (Zork Implementation Language)
				Franz Lisp
				Common Lisp		ANSI standard
				Le Lisp
				MIT Scheme
				XLISP
					T
					Chez Scheme
					Emacs Lisp
					AutoLISP
					PicoLisp
					Gambit
						EuLisp
						ISLISP
						OpenLisp
						PLT Scheme				Racket
						newLISP
						GNU Guile
								Visual LISP
									Clojure
									Arc
									LFE
										Hy
											Chialisp