/* Entry point of the parser.
Parse the regular expression REGEXP and return the structure tree.
- If an error is occured, ERR is set by error code, and return NULL.
+ If an error has occurred, ERR is set by error code, and return NULL.
This function build the following tree, from regular expression <reg_exp>:
CAT
/ \
/* This is intended for the expressions like "a{1,3}".
Fetch a number from `input', and return the number.
Return -1, if the number field is empty like "{,1}".
- Return -2, If an error is occured. */
+ Return -2, if an error has occurred. */
static int
fetch_number (re_string_t *input, re_token_t *token, reg_syntax_t syntax)