Erlang (programming language)/Tutorials/Yecc: Difference between revisions
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imported>Eric Evers (New page: Making Parsers with yecc Yecc is an erlang version of yacc. We have a BNF grammar in a source file ending in .yrl yrl means yecc rule list. We can parse simple a simple xhtml file using ...) |
imported>Eric Evers mNo edit summary |
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yrl means yecc rule list. | yrl means yecc rule list. | ||
We can parse simple a simple xhtml file using yecc. | We can parse simple a simple xhtml file using yecc. | ||
(Of course a more powerful way to xml in erlang is xmerl) | (Of course a more powerful way to do xml in erlang is xmerl) | ||
html.yrl source: | html.yrl source: | ||
Revision as of 12:46, 1 May 2008
Making Parsers with yecc
Yecc is an erlang version of yacc.
We have a BNF grammar in a source file ending in .yrl yrl means yecc rule list. We can parse simple a simple xhtml file using yecc. (Of course a more powerful way to do xml in erlang is xmerl)
html.yrl source:
Nonterminals tag elements element start_tag end_tag .
Terminals 'atom' '<' '>' '/'.
Rootsymbol tag.
tag ->
start_tag tag end_tag :
['$1', '$2', '$3'].
tag ->
start_tag tag tag end_tag :
['$1', '$2', '$3', '$4'].
tag ->
start_tag elements end_tag :
['$1', {'contents','$2'}, '$3'].
tag ->
start_tag end_tag :
['$1','$2'].
start_tag -> '<' 'atom' '>' : {'open','$2'}.
end_tag -> '<' '/' 'atom' '>' : {'close','$3'}.
elements -> element : ['$1'].
elements -> element elements : ['$1', '$2'].
element -> atom : '$1'.
% yecc:yecc("html.yrl","html_parser.erl").
% c(html_parser).
% f(B), {_,B,_} =
% erl_scan:string(
% "<html><head></head><body>hello_world</body></html>").
% html_parser:parse(B).