Parenthetic Expressions

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Epsilon User's Manual and Reference > Commands by Topic > Moving Around > Moving in Larger Units >

Parenthetic Expressions

Epsilon has commands to deal with matching parentheses, square brackets, and curly braces. We call a pair of these characters with text between them a level. You can use these level commands to manipulate expressions in many programming languages, such as Lisp, C, and Epsilon's own embedded programming language, EEL.

A level can contain other levels, and Epsilon won't get confused by the inner levels. For example, in the text "one (two (three) four) five" the string "(two (three) four)" constitutes a level. Epsilon recognizes that "(three)" also constitutes a level, and so avoids the mistake of perhaps calling "(two (three)" a level. In each level, the text inside the delimiters must contain matched pairs of that delimiter. In C mode, Epsilon knows to ignore delimiters inside strings or comments, when appropriate.

Epsilon recognizes the following pairs of enclosures: "(" and ")", "[" and "]", "{" and "}". The command Ctrl-Alt-F moves forward to the end of the next level, by looking forward until it sees the start of a level, and moving to its end. The command Ctrl-Alt-B moves backward by looking back for the end of a level and going to its beginning. The Ctrl-Alt-K command kills the next level by moving over text like Ctrl-Alt-F and killing as it travels, and the Alt-<Del> command moves backward like Ctrl-Alt-B and kills as it travels.

The Alt-) key runs the find-delimiter command. Use it to temporarily display a matching delimiter. The command moves backward like Ctrl-Alt-B and pauses for a moment, showing the screen, then restores the screen as before. The pause normally lasts one half of a second, or one second if the command must temporarily reposition the window to show the matching delimiter. You can specify the number of hundredths of a second to pause by setting the variables near-pause and far-pause . Also, typing any key will immediately restore the original window context, without further pause.

The show-matching-delimiter command inserts the key that invoked it by calling normal-character and then invokes find-delimiter to show its match. Some people like to bind the ")", "]" and "}" keys to show-matching-delimiter.

In some modes, when the cursor is over a delimiter Epsilon will automatically seek out its matching delimiter and highlight them both. See the descriptions of C, TeX, and HTML modes for more information.

Standard bindings:

Alt-)    find-delimiter

Ctrl-Alt-F    forward-level

Ctrl-Alt-B    backward-level

Ctrl-Alt-K    kill-level

Alt-<Del>    backward-kill-level

   show-matching-delimiter

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