Module: EBNF::Parser
- Included in:
- Base
- Defined in:
- lib/ebnf/parser.rb
Instance Method Summary collapse
-
#alt(s) ⇒ Array
Parse alt >>> alt(“a | b | c”) ((alt, [(‘id’, ‘a’), (‘id’, ‘b’), (‘id’, ‘c’)]), ”).
-
#diff(s) ⇒ Object
parse diff.
-
#eachRule(scanner) {|rule_string| ... } ⇒ Object
Iterate over rule strings.
-
#ebnf(s) ⇒ Array
Parse a string into an expression tree and a remaining string.
-
#postfix(s) ⇒ Object
parse postfix.
-
#primary(s) ⇒ Object
parse primary.
-
#ruleParts(rule) ⇒ Rule
Parse a rule into a rule number, a symbol and an expression.
-
#seq(s) ⇒ Object
parse seq.
-
#terminal(s) ⇒ Object
parse one terminal; return the terminal and the remaining string.
Instance Method Details
#alt(s) ⇒ Array
Parse alt
>>> alt("a | b | c")
((alt, \[('id', 'a'), ('id', 'b'), ('id', 'c')\]), '')
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# File 'lib/ebnf/parser.rb', line 117 def alt(s) debug("alt") {"(#{s.inspect})"} args = [] while !s.empty? e, s = depth {seq(s)} debug {"=> seq returned #{[e, s].inspect}"} if e.to_s.empty? break unless args.empty? e = [:seq, []] # empty sequence end args << e unless s.empty? t, ss = depth {terminal(s)} break unless t[0] == :alt s = ss end end args.length > 1 ? [args.unshift(:alt), s] : [e, s] end |
#diff(s) ⇒ Object
parse diff
>>> diff("a - b")
((diff, \[('id', 'a'), ('id', 'b')\]), '')
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# File 'lib/ebnf/parser.rb', line 172 def diff(s) debug("diff") {"(#{s.inspect})"} e1, s = depth {postfix(s)} debug {"=> postfix returned #{[e1, s].inspect}"} unless e1.to_s.empty? unless s.empty? t, ss = depth {terminal(s)} debug {"diff #{[t, ss].inspect}"} if t.is_a?(Array) && t.first == :diff s = ss e2, s = primary(s) unless e2.to_s.empty? return [[:diff, e1, e2], s] else error("diff", "Syntax Error") raise "Syntax Error" end end end end [e1, s] end |
#eachRule(scanner) {|rule_string| ... } ⇒ Object
Iterate over rule strings. a line that starts with ‘[’ or ‘@’ starts a new rule
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# File 'lib/ebnf/parser.rb', line 10 def eachRule(scanner) cur_lineno = 1 r = '' until scanner.eos? case when s = scanner.scan(%r(\s+)m) # Eat whitespace cur_lineno += s.count("\n") #debug("eachRule(ws)") { "[#{cur_lineno}] #{s.inspect}" } when s = scanner.scan(%r(/\*([^\*]|\*[^\/])*\*/)m) # Eat comments cur_lineno += s.count("\n") debug("eachRule(comment)") { "[#{cur_lineno}] #{s.inspect}" } when s = scanner.scan(%r(^@terminals)) #debug("eachRule(@terminals)") { "[#{cur_lineno}] #{s.inspect}" } yield(r) unless r.empty? @lineno = cur_lineno yield(s) r = '' when s = scanner.scan(/@pass/) # Found rule start, if we've already collected a rule, yield it #debug("eachRule(@pass)") { "[#{cur_lineno}] #{s.inspect}" } yield r unless r.empty? @lineno = cur_lineno r = s when s = scanner.scan(/\[(?=\w+\])/) # Found rule start, if we've already collected a rule, yield it yield r unless r.empty? #debug("eachRule(rule)") { "[#{cur_lineno}] #{s.inspect}" } @lineno = cur_lineno r = s else # Collect until end of line, or start of comment s = scanner.scan_until(%r((?:/\*)|$)m) cur_lineno += s.count("\n") #debug("eachRule(rest)") { "[#{cur_lineno}] #{s.inspect}" } r += s end end yield r unless r.empty? end |
#ebnf(s) ⇒ Array
Parse a string into an expression tree and a remaining string
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# File 'lib/ebnf/parser.rb', line 99 def ebnf(s) debug("ebnf") {"(#{s.inspect})"} e, s = depth {alt(s)} debug {"=> alt returned #{[e, s].inspect}"} unless s.empty? t, ss = depth {terminal(s)} debug {"=> terminal returned #{[t, ss].inspect}"} return [e, ss] if t.is_a?(Array) && t.first == :")" end [e, s] end |
#postfix(s) ⇒ Object
parse postfix
>>> postfix("a b c")
(('id', 'a'), ' b c')
>>> postfix("a? b c")
((opt, ('id', 'a')), ' b c')
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# File 'lib/ebnf/parser.rb', line 203 def postfix(s) debug("postfix") {"(#{s.inspect})"} e, s = depth {primary(s)} debug {"=> primary returned #{[e, s].inspect}"} return ["", s] if e.to_s.empty? if !s.empty? t, ss = depth {terminal(s)} debug {"=> #{[t, ss].inspect}"} if t.is_a?(Array) && [:opt, :star, :plus].include?(t.first) return [[t.first, e], ss] end end [e, s] end |
#primary(s) ⇒ Object
parse primary
>>> primary("a b c")
(('id', 'a'), ' b c')
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# File 'lib/ebnf/parser.rb', line 223 def primary(s) debug("primary") {"(#{s.inspect})"} t, s = depth {terminal(s)} debug {"=> terminal returned #{[t, s].inspect}"} if t.is_a?(Symbol) || t.is_a?(String) [t, s] elsif %w(range hex).map(&:to_sym).include?(t.first) [t, s] elsif t.first == :"(" e, s = depth {ebnf(s)} debug {"=> ebnf returned #{[e, s].inspect}"} [e, s] else ["", s] end end |
#ruleParts(rule) ⇒ Rule
Parse a rule into a rule number, a symbol and an expression
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# File 'lib/ebnf/parser.rb', line 57 def ruleParts(rule) num_sym, expr = rule.split('::=', 2).map(&:strip) num, sym = num_sym.split(']', 2).map(&:strip) num = num[1..-1] r = Rule.new(sym && sym.to_sym, num, ebnf(expr).first, :ebnf => self) debug("ruleParts") { r.inspect } r end |
#seq(s) ⇒ Object
parse seq
>>> seq("a b c")
((seq, \[('id', 'a'), ('id', 'b'), ('id', 'c')\]), '')
>>> seq("a b? c")
((seq, \[('id', 'a'), (opt, ('id', 'b')), ('id', 'c')\]), '')
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# File 'lib/ebnf/parser.rb', line 145 def seq(s) debug("seq") {"(#{s.inspect})"} args = [] while !s.empty? e, ss = depth {diff(s)} debug {"=> diff returned #{[e, ss].inspect}"} unless e.to_s.empty? args << e s = ss else break; end end if args.length > 1 [args.unshift(:seq), s] elsif args.length == 1 args + [s] else ["", s] end end |
#terminal(s) ⇒ Object
parse one terminal; return the terminal and the remaining string
A terminal is represented as a tuple whose 1st item gives the type; some types have additional info in the tuple.
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# File 'lib/ebnf/parser.rb', line 258 def terminal(s) s = s.strip case m = s[0,1] when '"', "'" l, s = s[1..-1].split(m, 2) [l, s] when '[' l, s = s[1..-1].split(']', 2) [[:range, l], s] when '#' s.match(/(#\w+)(.*)$/) l, s = $1, $2 [[:hex, l], s] when /[[:alpha:]]/ s.match(/(\w+)(.*)$/) l, s = $1, $2 [l.to_sym, s] when '@' s.match(/@(#\w+)(.*)$/) l, s = $1, $2 [[:"@", l], s] when '-' [[:diff], s[1..-1]] when '?' [[:opt], s[1..-1]] when '|' [[:alt], s[1..-1]] when '+' [[:plus], s[1..-1]] when '*' [[:star], s[1..-1]] when /[\(\)]/ [[m.to_sym], s[1..-1]] else error("terminal", "unrecognized terminal: #{s.inspect}") raise "Syntax Error" end end |