emacs: External Lisp
27.11 Running an External Lisp
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Lisp mode is the major mode for editing programs written in
general-purpose Lisp dialects, such as Common Lisp. Its mode command is
‘M-x lisp-mode’. Emacs uses Lisp mode automatically for files whose
names end in ‘.l’, ‘.lsp’, or ‘.lisp’.
You can run an external Lisp session as a subprocess or “inferior
process” of Emacs, and pass expressions to it to be evaluated. To begin
an external Lisp session, type ‘M-x run-lisp’. This runs the program
named ‘lisp’, and sets it up so that both input and output go through an
Emacs buffer named ‘*inferior-lisp*’. To change the name of the Lisp
program run by ‘M-x run-lisp’, change the variable
‘inferior-lisp-program’.
The major mode for the ‘*lisp*’ buffer is Inferior Lisp mode, which
combines the characteristics of Lisp mode and Shell mode (
Shell
Mode). To send input to the Lisp session, go to the end of the
‘*lisp*’ buffer and type the input, followed by <RET>. Terminal output
from the Lisp session is automatically inserted in the buffer.
When you edit a Lisp program in Lisp mode, you can type ‘C-M-x’
(‘lisp-eval-defun’) to send an expression from the Lisp mode buffer to a
Lisp session that you had started with ‘M-x run-lisp’. The expression
sent is the top-level Lisp expression at or following point. The
resulting value goes as usual into the ‘*inferior-lisp*’ buffer. Note
that the effect of ‘C-M-x’ in Lisp mode is thus very similar to its
effect in Emacs Lisp mode (Lisp Eval), except that the
expression is sent to a different Lisp environment instead of being
evaluated in Emacs.
The facilities for editing Scheme code, and for sending expressions
to a Scheme subprocess, are very similar. Scheme source files are
edited in Scheme mode, which can be explicitly enabled with ‘M-x
scheme-mode’. You can initiate a Scheme session by typing ‘M-x
run-scheme’ (the buffer for interacting with Scheme is named
‘*scheme*’), and send expressions to it by typing ‘C-M-x’.
Info Catalog
emacs: Lisp Interaction
emacs: Building