Class: Peggy::Builder

Inherits:
Parser
  • Object
show all
Defined in:
lib/parse/builder.rb

Overview

Parser builder. The built in methods create syntax elements. Any other method called on this object create references to production, or actual productions, if called at the top level. Todo: Change to a class and separate from Parser.

Direct Known Subclasses

ABNF, ABNF::ABNFParser

Instance Attribute Summary collapse

Attributes inherited from Parser

#debug_flag, #ignore_productions, #parse_results, #source_text

Instance Method Summary collapse

Methods inherited from Parser

#_memoize, #allow?, #ast?, #check?, #correct_regexp!, #dissallow?, #ignore?, #literal?, #match?, #query?, #regexp?, #string?

Constructor Details

#initialize ⇒ Builder

Constructor



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# File 'lib/parse/builder.rb', line 324

def initialize
  reset!
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(name, *args) ⇒ Object

Create a production if at the top level, or a reference to a production a production is being built.



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# File 'lib/parse/builder.rb', line 341

def method_missing name, *args
  if @building
    if @parent
      ref = Reference.new name
      @parent << ref
    elsif block_given?
      prod = Production.new name
      @parent = prod
      yield
      @parent = nil
      @productions[name] = prod
    else
      super
    end
  else
    prod = @productions[name]
# pp name.inspect, @productions.keys unless prod
    super unless prod
# puts "matching #{name} at #{args.first}"
    prod.match self, args.first
  end
end

Instance Attribute Details

#parent ⇒ Object (readonly)

Current parent being built



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# File 'lib/parse/builder.rb', line 321

def parent
  @parent
end

#productions ⇒ Object (readonly)

Productions to build



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# File 'lib/parse/builder.rb', line 319

def productions
  @productions
end

Instance Method Details

#[](index) ⇒ Object

Reference a production by its name index.



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# File 'lib/parse/builder.rb', line 335

def [] index
  productions[index]
end

#alt(&blk) ⇒ Object Also known as: one

Build an Alternatives element.



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# File 'lib/parse/builder.rb', line 365

def alt &blk
  build_piece Alternatives, blk
end

#eof(*args) ⇒ Object

Build or match the end of file element. If currently building, a Reference to eof is built. Otherwise eof is matched.



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# File 'lib/parse/builder.rb', line 373

def eof *args
  if @building
    method_missing :eof, *args
  else
    super args.first
  end
end

#lit(*values) ⇒ Object

Add an Literal element to the parent.



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# File 'lib/parse/builder.rb', line 389

def lit *values
  if values.size == 1
    build_piece Literal, nil, values.first
  else
    one{
      for v in values
        build_piece Literal, nil, v
      end
    }
  end
end

#many(&blk) ⇒ Object

Build an AnyNumber element.



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# File 'lib/parse/builder.rb', line 402

def many &blk
  build_piece AnyNumber, blk
end

#neg(&blk) ⇒ Object

Build a negative predicate. Use when you want to make sure the enclosed element is not present. The cursor is not advanced for predicates.



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# File 'lib/parse/builder.rb', line 418

def neg &blk
  build_piece Negative, blk
end

#opt(&blk) ⇒ Object

Build an Optional element.



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# File 'lib/parse/builder.rb', line 407

def opt &blk
  build_piece Optional, blk
end

#parse?(goal, source = nil, index = 0) ⇒ Boolean

Invokes the parser from the beginning of the source on the given production goal. You may provide the source here or you can set source_text prior to calling. If index is provided the parser will ignore characters previous to it.

Returns:

  • (Boolean) 


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# File 'lib/parse/builder.rb', line 431

def parse? goal, source=nil, index=0
  @building = nil
  super
end

#pos(&blk) ⇒ Object

Build a positive predicate. Use when you want to make sure the enclosed element is present. If matched the cursor is not advanced.



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# File 'lib/parse/builder.rb', line 424

def pos &blk
  build_piece Positive, blk
end

#reset! ⇒ Object

Clear the parser and prepare it for a new parse.



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# File 'lib/parse/builder.rb', line 329

def reset!
  @building = true
  @productions = {}
end

#seq(&blk) ⇒ Object Also known as: each

Build a Sequence element.



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# File 'lib/parse/builder.rb', line 382

def seq &blk
  build_piece Sequence, blk
end

#some(&blk) ⇒ Object

Build an AtLeastOne element.



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# File 'lib/parse/builder.rb', line 412

def some &blk
  build_piece AtLeastOne, blk
end

#to_s ⇒ Object

Convert productions to Peggy grammar. This is notable to out put any Ruby parse methods, only grammars built with Builder methods.



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# File 'lib/parse/builder.rb', line 438

def to_s
  productions.values.join "\n"
end