Created
February 5, 2013 23:48
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composing parslet parsers
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require 'rubygems' | |
require 'parslet' | |
#This needs a few more 'as' calls to annotate the output | |
class JSONParser < Parslet::Parser | |
def initialize(number_parser) | |
@number_parser | |
end | |
rule(:space) { match('[\s\n]').repeat(1)} | |
rule(:space?) { space.maybe } | |
rule(:digit) { match('[0-9]') } | |
rule(:hexdigit) { match('[0-9a-fA-F]') } | |
rule(:comma) { space? >> str(',') >> space? } | |
rule(:colon) { space? >> str(':') >> space? } | |
rule(:number) { @number_parser } | |
rule(:escaped_character) { str('\\') >> (match('["\\\\/bfnrt]') | (str('u') >> hexdigit.repeat(4,4))) } | |
rule(:string){ | |
str('"') >> ( | |
escaped_character | str('"').absent? >> any) | |
).repeat.as(:string) >> str('"') | |
} | |
rule(:value){ | |
(string | | |
number | | |
object | | |
array | | |
str('true').as(:true) | | |
str('false').as(:false) | | |
str('null').as(:null)).as(:val) | |
} | |
rule(:entry) { string >> colon >> value } | |
rule(:pair_list) { entry>> (comma >> entry).repeat } | |
rule(:object) { str('{') >> space? >> pair_list.maybe >> space? >> str('}') } | |
rule(:value_list) { value >> (comma >> value).repeat } | |
rule(:array) { str('[') >> space? >> value_list.maybe >> space? >> str(']')} | |
rule(:json) { space? >> value >> space?} | |
root(:json) | |
end | |
class NumberParser < ParsletParser | |
rule(:space) { match('[\s\n]').repeat(1)} | |
rule(:space?) { space.maybe } | |
rule(:digit) { match('[0-9]') } | |
rule(:number) {space? >> str('-').maybe >> | |
(str('0') | (match('[1-9]') >> digit.repeat)) >> | |
(str('.') >> digit.repeat).maybe >> | |
((str('e')| str('E')) >> (str('+')|str('-')).maybe >> digit.repeat ).maybe} | |
root(:number) | |
end | |
json_parser = JSONParser.new(NumberParser.new) |
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Nigel, just a quick note to say thanks for your help... used your suggestion and it fits my needs perfectly, most appreciated.