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