: Learning GNU Emacs, 3rd Edition

8.5.1 Matching Braces

8.5.1 Matching Braces

LATEX commands often take the form keyword{text}. LaTeX mode doesn't try to figure out if you're using the "right" keywords since the language is extensible and you may have defined your own keywords. It does, however, provide support for avoiding the most common error: mismatched curly braces and dollar signs.

In LATEX , curly braces ({}) and dollar signs ($$) should always appear in pairs; Emacs checks to make sure that each opening brace or dollar sign has a counterpart. When you type a closing brace or dollar sign, the cursor moves quickly to its counterpart (provided that it is on the screen; it shows the context in the minibuffer if it is not), then back again.

Emacs generates braces in matching pairs. The command C-c { inserts opening and closing braces and positions the cursor for typing between the braces.

Typing C-c } moves you past the right brace. It always finds the correct closing brace, given your current position. If there is no closing brace, you get an error message that says Scan error: Unbalanced parentheses. You also get this error message if you type C-c } while the cursor is in a section that is not surrounded by braces, which can be a little confusing.

To check for mismatched curly braces and dollar signs, type M-x tex-validate-buffer Enter. This command checks the entire buffer for unbalanced parentheses, curly braces, dollar signs, and the like. (If you have a large file, you might want to validate a region instead using M-x tex-validate-region Enter). If it finds any errors, Emacs displays an *Occur* buffer with Mismatches: at the top and a list of lines on which it found errors. You can then easily move to each line that contains an error with M-x goto-line.

Sometimes a mismatched parenthesis early in the buffer can start a chain reaction of "errors" through the rest of the file. If you suspect that one of the corrections you make may have fixed most of the remaining errors, simply run tex-validate-buffer again.

When you're stepping through errors, C-c } provides a good way to check where the closing brace for a given opening brace is. Position the cursor right after the opening brace and press C-c }.


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