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3.6.2 The Range Operator (-)

Regex recognizes range expressions inside a list. They represent those characters that fall between two elements in the current collating sequence. You form a range expression by putting a range operator between two characters.(3) `-' represents the range operator. For example, `a-f' within a list represents all the characters from `a' through `f' inclusively.

If the syntax bit RE_NO_EMPTY_RANGES is set, then if the range's ending point collates less than its starting point, the range (and the regular expression containing it) is invalid. For example, the regular expression `[z-a]' would be invalid. If this bit isn't set, then Regex considers such a range to be empty.

Since `-' represents the range operator, if you want to make a `-' character itself a list item, you must do one of the following:

For example, `[-a-z]' matches a lowercase letter or a hyphen (in English, in ASCII).

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