This page is about evaluating EmacsLisp '''S-expressions''', or '''sexps'''. A [[sexp]] is any readable Lisp expression -- code enclosed in parentheses, a string enclosed in double quotes, a variable name, a quoted expression, a numeral, and so on. See also the sections "How to Evaluate" in the EmacsLispIntro and "Evaluating Emacs Lisp Expressions" in the EmacsManual. ; ##C-x C-e##: When looking at EmacsLisp code, put the [[cursor]] after a [[sexp]], and hit `C-x C-e' (command `eval-last-sexp'). This prints the value of the sexp in the [[echo area]]. If you need to look at the result again later, you can find it in [[buffer]] `*Messages*' (for a while). : You can insert the result of an evaluation into the current buffer at [[point]] by using a [[prefix argument]]: `C-u C-x C-e'. This can be useful if you are writing some code that uses the result. ; ##C-M-x##: In EmacsLispMode (e.g., when in a file buffer `##*.el##'), you can use `C-M-x' (command `eval-defun') which evaluates the defun at point. Note that the function name is a bit of a misnomer: invoking `eval-defun' evaluates the top-level sexp containing point, irrespective of use of defun. If the [[cursor]] is inside or immediately after a [[variable]] declaration, then this function, unlike `C-x C-e', resets the variable to the value contained in the declaration. ; ##M-x eval-region##: You can evaluate the EmacsLisp code in the [[region]] using `M-x eval-region'. To evaluate all of the code in the current [[buffer]], mark it using `C-x h', then do `M-x eval-region'. For information about loading EmacsLisp library files, see InstallingPackages. ; ##C-h v##: If you just want to check the current value of a variable, the easiest way is to use `C-h v' (command `describe-variable'). This prints the [[variable]]'s [[doc string]] and [[symbol value|value]]. ; ##M-x set-variable##: You can set [[user option]]s using ‘M-x set-variable’. This can be quicker than evaluating an assignment sexp: `##M-: (setq my-variable some-value)##'. ; ##M-:##: You can evaluate any [[sexp]] using `##M-:##' (command `eval-expression', by default). : This prompts you to type a sexp in the [[minibuffer]]. The sexp is evaluated and the result is shown in the [[echo area]] (or inserted into the current buffer if you use a [[prefix argument]]). : This is especially useful when you are coding and testing. It lets you quickly invoke non-interactive functions (non-[[command]]s). It saves you from typing them into a buffer and using `C-x C-e' to evaluate them. [:PrettyPrintEvalExpression] == Pretty-Printing for M-: == To make `##M-:##' pretty-print: (global-set-key [remap eval-expression] 'pp-eval-expression) or for Emacs before 22 (substitute-key-definition 'eval-expression 'pp-eval-expression global-map) To make `C-x C-e' pretty-print: (global-set-key [remap eval-last-sexp] 'pp-eval-last-sexp) or for Emacs before 22 (substitute-key-definition 'eval-last-sexp 'pp-eval-last-sexp global-map) These replace all `global-map' bindings for `eval-*' by the corresponding `pp-eval-*'. This means that the result of a [[sexp]] evaluation is pretty-printed in a separate [[buffer]], `##*Pp Eval Output*##'. You can edit the definition there, or copy it to other EmacsLisp code. Some people like to use InferiorEmacsLispMode -- `M-x ielm'. This creates a buffer much like a shell buffer. Whatever Lisp expressions you type are evaluated and the result is printed into the buffer. Similarly, you can use buffer `##*scratch*##' much as you would a buffer in EmacsLispMode. However, by default the mode of `##*scratch*##' is LispInteractionMode, which is slightly different from EmacsLispMode. In particular, `C-j' acts quite differently. If you want to evaluate a region and insert the result of each top-level form as a comment (similar to code snippets in the EmacsLispManual), use [https://github.com/lewang/le_emacs_libs/blob/master/le-eval-and-insert-results.el le-eval-and-insert-results.el] == See Also == [:PpPlus] Library '''PpPlus''' ('''[[pp+.el]]''') enhances pretty-printing in several ways. ---- CategoryCode