Lambda Logo Tour

By Xah Lee. Date: . Last updated: .

A Lambda Logo Tour (and why LISP languages using λ as logo should not be looked upon kindly)

Dear lispers,

The lambda character λ, always struck a awe in me, as with other mathematical symbols. In my mind, i imagine that those obscure math symbolism are etched in stone by god. A salient example is the book cover Concrete Mathematics by Ronald Graham et al.

Concrete Mathematics TpXbC-s1000
Concrete Mathematics by Ronald Graham, Knuth, Patashnik. Buy at amazon 3024×4032

Here we see the summation sign etched in stone. The summation sign happens to be my favorite math symbol. (chosen as my website signet: xah lee sum logo 2000 )

These symbols are not to be trifled with. If anyone puffs in as much half a snicker, i wish god strikes a thunder upon their impudence.

The Greek lambda symbol is used in a branch of logic called lambda calculus. The theories of lambda calculus is what functional languages are based on, thus many functional language's logo features the lambda. Here is a collection of functional language's logos involving the lambda.

Mit Scheme lisp logo
MIT Scheme's logo.

MIT Scheme is the grand daddy of Scheme lisp. Its logo features a recursive shield with lambda. •'s logo's logo.'s logo has a modern look. It is a simple lambda inside a O figuration. Though, i was told this “O” is supposed to be a pair of parenthesis.

plt scheme lisp logo 1996 Grateful Dead - Steal Your Face
PLT Scheme's first logo, ~1996, and Grateful Dead's logo 1976.

PLT Scheme's first logo was based on rock band Grateful Dead's album Steal Your Face design. The album is released in 1976. Cover was designed by Owsley Stanley and artist Bob Thomas, and was originally used as a logo to mark the band's equipment.

plt scheme lisp logo steal-your-face
PLT Scheme's first logo design.

[The Many Faces of DrRacket By Robby Findler. At , accessed on 2015-10-08 ]

PLT Scheme logo
PLT Scheme's logo, ~2000

PLT Scheme's logo, notable is the red/white/blue coloring scheme.

MzScheme's logo.

MzScheme is the name of the actual compiler of PLT Scheme. Now named Racket. The logo features a lambda besides a Chinese character 文 (wén). The character means written language.

PLT Scheme changed its name to Racket in 2010-06
plt scheme lisp horse logo
PLT scheme lisp horse logo. (i don't remember where this is used.)

racket lang logo wjwxd
racket lang logo, around 2017, by Matthew Butterick?
Common Lisp HTTP server logo
cl-http web badge. Quite lame and unprofessional.
Scheme Shell logo
Scheme shell scsh logo is a lambda inside a bivalve, perhaps most florid of the bunch:
Haskell Logo 2003-05 Fritz Ruehr
Haskell logo, since 2003-05. It is designed by Fritz Ruehr []. Superb.
xah haskell logo 2022-01-01 d8HsW Haskell web badge
Two web badges for Haskell. (For detail, see Haskell Logo.)

The book cover of Structure and Interpretation of Computer Programs , by Harold Abelson, Gerald Jay Sussman, features a wizard and witch gesticulating with prominent lambda, and a monster foot of the table showing.

I love these lambda-featuring logos. However, i have a complaint. As most of you know, lisp languages are not purely functional languages. Subroutines in lisps easily have side-effects, and sometimes non-functional programing methodologies such as OOP are actually encouraged in lisp. As most of you know, the lambda symbol chosen by functional languages is to signify no side-effects. In this respect, i find the lisp languages not totally deserving the use of lambda in their logo. As i have expressed before, mathematical symbols are not to be trifled with, and the Schemers have tainted my mathematics, strictly speaking.

Although i have this minor objection with lispers using the lambda symbol, but overall i think the lispers and i share a more important common goal. That is, to wipe out all imperative programing ignoramuses of the world. Once the unix and C and Perl and otherwise idiots are all dead, then i'll formally raise my objection about Lisper's unfit borrowing of the lambda symbol.


PFP logo, by Martin Erwig.

The PFP library for Haskell features a lambda disguised as a histogram. One of the most well-designed among lambda logos. (“A Probabilistic Functional Programming Library for Haskell” by Martin Erwig and Steve Kollmansberger, 2005.

FC++ logo
Logo for FC++ by Brian Dickens.

Someone has written a C++ library for functional programing, called FC++. (by Brian McNamara and Yannis Smaragdakis, 2003) Website:

Scheme Chicken logo
Chicken Scheme logo.

Chicken Scheme features a logo that is a lambda inside a hen silhouette. (by Felix L Winkelmann, at

This is getting silly and disrespectful.

chicken scheme logo chicken4-low
Chicken's new logos, by Moe Aboulkheir et al. Left as of , right as of .

I prefer the original yellow hen logo. This new modern-looking logo lost its soul. You can't easily tell what bird it is, and the funky lambda takes some tech geeking to recognize. The original logo of the fat hen signifies birth, with lambda right in its tummy, and fits well with the project's comical name Chicken Scheme. This is a example where logo with elegant artwork is worse.

For some history of CHICKEN scheme's logo, see

Qi logo
A Qi programming language logo designed by yours truely. For detail, see: Qi Language Logo.
Clojure logo
Logo of Clojure, a new Lisp lang in Java Virtual Machine. The logo is designed by Tom Hickey with input from Rich Hickey.

[see Clojure Tutorial]

Non-Lambda Logos

here's lisp logos that do not involve lambda.

LISP logo
Classic twisty lisp logo. [see LISP Logo]
CLforJava logo
CLforJava logo.

CLforJava is a Common Lisp implementation on Java Virtual Machine. Home page: [ ].

Clozure Common Lisp logo
Clozure Common Lisp logo.

Clozure Common Lisp is formally OpenMCL, which is derived from Macintosh Common Lisp (MCL). Home page is at: ,

Brown University PLT lambda logo 2017 06 23
Brown University PLT lambda logo, 2017-06-23