Emacs Init: Display Lambda as λ

By Xah Lee. Date: . Last updated: .

Show Lambda As λ

Alt+x prettify-symbols-mode

Display the word “lambda” as λ, in current buffer.

(New in Emacs 24.4 (Released 2014-10).)

Alt+x global-prettify-symbols-mode

Globally. Put this in your Emacs Init File: 

(global-prettify-symbols-mode 1)
emacs pretty lambda 2021-09-25 g9TW
emacs pretty lambda 2021-09-25

Add Support for Pretty Symbols Mode

prettify-symbols-mode only works for major modes that supports it.

To add support, in your major mode, do:

(setq prettify-symbols-alist '(("lambda" . 955)))

The 955 is Unicode codepoint for λ in decimal. 〔see Emacs: Get Char Info. Name, Position, Font, Encoding, Syntax, Etc〕

You can add other pairs. For example, to have arrow, do:

(setq prettify-symbols-alist
      '(
        ("lambda" . 955) ; λ
        ("->" . 8594)    ; →
        ("=>" . 8658)    ; ⇒
        ("map" . 8614)    ; ↦
        ))

You can add it as a Hook for any major mode. Here's a example:

(defun my-add-pretty-symbol ()
  "make some word display as Unicode symbols"
  (setq prettify-symbols-alist
        '(
          ("lambda" . 955) ; λ
          ("->" . 8594)    ; →
          ("=>" . 8658)    ; ⇒
          ("map" . 8614)   ; ↦
          )))

(add-hook 'clojure-mode-hook 'my-add-pretty-symbol)
(add-hook 'haskell-mode-hook 'my-add-pretty-symbol)
(add-hook 'tex-mode-hook 'my-add-pretty-symbol)

For other math symbols you might want to add, see:

Emacs, font setup