84 lines
2.3 KiB
Ruby
84 lines
2.3 KiB
Ruby
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# Matches a parslet repeatedly.
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#
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# Example:
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#
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# str('a').repeat(1,3) # matches 'a' at least once, but at most three times
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# str('a').maybe # matches 'a' if it is present in the input (repeat(0,1))
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#
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class Parslet::Atoms::Repetition < Parslet::Atoms::Base
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attr_reader :min, :max, :parslet
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def initialize(parslet, min, max, tag=:repetition)
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super()
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raise ArgumentError,
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"Asking for zero repetitions of a parslet. (#{parslet.inspect} repeating #{min},#{max})" \
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if max == 0
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@parslet = parslet
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@min, @max = min, max
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@tag = tag
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@error_msgs = {
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:minrep => "Expected at least #{min} of #{parslet.inspect}",
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:unconsumed => "Extra input after last repetition"
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}
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end
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def try(source, context, consume_all)
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occ = 0
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accum = [@tag] # initialize the result array with the tag (for flattening)
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start_pos = source.pos
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break_on = nil
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loop do
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success, value = parslet.apply(source, context, false)
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break_on = value
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break unless success
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occ += 1
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accum << value
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# If we're not greedy (max is defined), check if that has been reached.
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return succ(accum) if max && occ>=max
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end
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# Last attempt to match parslet was a failure, failure reason in break_on.
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# Greedy matcher has produced a failure. Check if occ (which will
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# contain the number of successes) is >= min.
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return context.err_at(
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self,
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source,
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@error_msgs[:minrep],
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start_pos,
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[break_on]) if occ < min
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# consume_all is true, that means that we're inside the part of the parser
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# that should consume the input completely. Repetition failing here means
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# probably that we didn't.
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#
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# We have a special clause to create an error here because otherwise
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# break_on would get thrown away. It turns out, that contains very
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# interesting information in a lot of cases.
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#
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return context.err(
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self,
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source,
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@error_msgs[:unconsumed],
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[break_on]) if consume_all && source.chars_left>0
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return succ(accum)
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end
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precedence REPETITION
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def to_s_inner(prec)
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minmax = "{#{min}, #{max}}"
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minmax = '?' if min == 0 && max == 1
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parslet.to_s(prec) + minmax
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end
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end
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