Class: Parslet::Atoms::Repetition

Inherits:
Base
  • Object
show all
Defined in:
lib/parslet/atoms/repetition.rb,
lib/parslet/atoms/visitor.rb

Overview

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))

Constant Summary

Constants included from Precedence

Precedence::ALTERNATE, Precedence::BASE, Precedence::LOOKAHEAD, Precedence::OUTER, Precedence::REPETITION, Precedence::SEQUENCE

Instance Attribute Summary collapse

Attributes inherited from Base

#label

Instance Method Summary collapse

Methods inherited from Base

#apply, #cached?, #inspect, #parse, #parse_with_debug, precedence, #setup_and_apply, #to_s

Methods included from CanFlatten

#flatten, #flatten_repetition, #flatten_sequence, #foldl, #merge_fold, #warn_about_duplicate_keys

Methods included from DSL

#>>, #absent?, #as, #capture, #ignore, #maybe, #present?, #repeat, #|

Constructor Details

#initialize(parslet, min, max, tag = :repetition) ⇒ Repetition

Returns a new instance of Repetition.

Raises:

  • (ArgumentError) 


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# File 'lib/parslet/atoms/repetition.rb', line 11

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 = min
  @max = max
  @tag = tag
end

Instance Attribute Details

#max ⇒ Object (readonly)

Returns the value of attribute max.



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# File 'lib/parslet/atoms/repetition.rb', line 10

def max
  @max
end

#min ⇒ Object (readonly)

Returns the value of attribute min.



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# File 'lib/parslet/atoms/repetition.rb', line 10

def min
  @min
end

#parslet ⇒ Object (readonly)

Returns the value of attribute parslet.



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# File 'lib/parslet/atoms/repetition.rb', line 10

def parslet
  @parslet
end

Instance Method Details

#accept(visitor) ⇒ Object

Call back visitors #visit_repetition method. See parslet/export for an example.



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# File 'lib/parslet/atoms/visitor.rb', line 51

def accept(visitor)
  visitor.visit_repetition(@tag, min, max, parslet)
end

#error_msgs ⇒ Object 



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# File 'lib/parslet/atoms/repetition.rb', line 25

def error_msgs
  @error_msgs ||= {
    minrep: "Expected at least #{min} of #{parslet.inspect}",
    unconsumed: 'Extra input after last repetition'
  }
end

#to_s_inner(prec) ⇒ Object 



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# File 'lib/parslet/atoms/repetition.rb', line 80

def to_s_inner(prec)
  minmax = "{#{min}, #{max}}"
  minmax = '?' if min == 0 && max == 1

  parslet.to_s(prec) + minmax
end

#try(source, context, consume_all) ⇒ Object 



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# File 'lib/parslet/atoms/repetition.rb', line 32

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