Tahir Hassan's Blog

My Technical Notes

Thursday, 17 March 2016

ELisp: Writing and Evaluating Code

Using ielm Repl

You can start it by M-x ielm This will switch the current window to a new ielm buffer. This is a simple repl in which you can write statements and press enter.

Using a buffer (not ielm)

Within for example, the *scratch* buffer (or any other lisp buffer for that matter), we can write our code and evaluate it; evaluations are printed in the *Messages* buffer. If we have *scratch* and *Messages* buffers open in two separate windows, and we can evaluate the code in *scratch* and see the results immediately in *Messages*.

Keybindings for Evaluation

The following keybindings hold when we are in Lisp Interaction mode:

• C-x C-e our cursor must be after the close-paren of the expression we want to evaluate. The result populates the minibuffer and the *Messages* buffer.
• C-M-x will execute the "root" expression that we are currently in. Just like C-x C-e, it will populate the minibuffer and the *Messages* buffer.
• C-j our cursor must be after the close-paren. This will execute the expression and populate the *scratch* buffer.