Amend parse-partial-sexp correctly to handle two character comment delimiters
Do this by adding a new field to the parser state: the syntax of the last character scanned, should that be the first char of a (potential) two char construct, nil otherwise. This should make the parser state complete. Also document element 9 of the parser state. Also refactor the code a bit. * src/syntax.c (struct lisp_parse_state): Add a new field. (SYNTAX_FLAGS_COMSTARTEND_FIRST): New function. (internalize_parse_state): New function, extracted from scan_sexps_forward. (back_comment): Call internalize_parse_state. (forw_comment): Return the syntax of the last character scanned to the caller when that character might be the first of a two character construct. (Fforward_comment, scan_lists): New dummy variables, passed to forw_comment. (scan_sexps_forward): Remove a redundant state parameter. Access all `state' information via the address parameter `state'. Remove the code which converts from external to internal form of `state'. Access buffer contents only from `from' onwards. Reformulate code at the top of the main loop correctly to recognize comment openers when starting in the middle of one. Call forw_comment with extra argument (for return of syntax value of possible first char of a two char construct). (Fparse_partial_sexp): Document elements 9, 10 of the parser state in the doc string. Clarify the doc string in general. Call internalize_parse_state. Take account of the new elements when consing up the output parser state. * doc/lispref/syntax.texi: (Parser State): Document element 9 and the new element 10. Minor wording corrections (remove reference to "trivial cases"). (Low Level Parsing): Minor corrections. * etc/NEWS: Note new element 10, and documentation of element 9 of parser state.
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