Class: Optimus::ParsedCalculator::ExpressionParser

Inherits:
Object
  • Object
show all
Extended by:
RParsec::Parsers
Includes:
RParsec::Parsers
Defined in:
lib/parsed_calculator.rb

Instance Method Summary collapse

Constructor Details

#initialize ⇒ ExpressionParser

Returns a new instance of ExpressionParser.



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# File 'lib/parsed_calculator.rb', line 26

def initialize
  @operators = RParsec::Operators.new(
    %w{+ - * / % & ( ) not and or = != > >= < <=}
  )
  expr = nil
  lazy_expr = lazy { expr }
  atom = (
    token(:str) { |lex| StringLiteral.new(lex) } |
    token(:number) { |lex| NumberLiteral.new(lex) } |
    token(:column) { |lex| ColumnReference.new(lex) } )
  
  lit = atom | (@operators['('] >> lazy_expr << @operators[')'])
  
  # Follows hte standard C 
  table = RParsec::OperatorTable.new.
    prefix(@operators['-'] >>   lambda {|a| -a}, 50).
    prefix(@operators['not'] >> lambda {|a| a.logical_not}, 50).
    infixl(@operators['*'] >>   lambda {|a, b| a*b}, 30).
    infixl(@operators['/'] >>   lambda {|a, b| a/b}, 30).
    infixl(@operators['%'] >>   lambda {|a, b| a%b}, 30).
    infixl(@operators['+'] >>   lambda {|a, b| a+b}, 27).
    infixl(@operators['-'] >>   lambda {|a, b| a-b}, 27).
    infixl(@operators['&'] >>   lambda {|a, b| a&b}, 25).
    infixl(@operators['>'] >>   lambda {|a, b| a>b}, 17).
    infixl(@operators['>='] >>  lambda {|a, b| a>=b}, 17).
    infixl(@operators['<'] >>   lambda {|a, b| a<b}, 17).
    infixl(@operators['<='] >>  lambda {|a, b| a<=b}, 17).
    infixl(@operators['='] >>   lambda {|a, b| a.eq(b)}, 15).
    infixl(@operators['!='] >>  lambda {|a, b| a.neq(b)}, 15).
    infixl(@operators['and'] >> lambda {|a, b| a.logical_and(b)}, 5).
    infixl(@operators['or'] >>  lambda {|a, b| a.logical_or(b)}, 4)
  
  expr = RParsec::Expressions.build(lit, table)
  
  lexeme = tokenizer.lexeme(whitespaces) << eof
  @parser = lexeme.nested(expr << eof)
end

Instance Method Details

#parse(str) ⇒ Object 



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# File 'lib/parsed_calculator.rb', line 64

def parse(str)
  begin
    @parser.parse(str)
  rescue Exception
    raise
  end
end