Class: ConstraintParser::Lexer

Inherits:
Object
  • Object
show all
Defined in:
lib/lexer.rb

Constant Summary collapse

AND = 
/AND/
CASCADE = 
/CASCADE/
CHECK = 
/CHECK/
COMMA = 
/,/
DELETE = 
/DELETE/
EQ = 
/\=/
FOREIGN_KEY = 
/FOREIGN KEY/
GT = 
/\>/
GTEQ = 
/\>=/
IDENT = 
/[a-zA-Z][a-zA-Z0-9_]*/
INT = 
/[0-9]+/
LPAREN = 
/\(/
LT = 
/\</
LTEQ = 
/\<=/
MATCH_OP = 
/~~/
NEQ = 
/\<\>/
NEWLINE = 
/\n/
ON = 
/ON/
PLUS = 
/\+/
PRIMARY_KEY = 
/PRIMARY KEY/
REFERENCES = 
/REFERENCES/
RESTRICT = 
/RESTRICT/
RPAREN = 
/\)/
SPACE = 
/[\ \t]+/
STRLIT = 
/\'(\\.|[^\\'])*\'/
TYPE = 
/::/
UNIQUE = 
/UNIQUE/

Instance Method Summary collapse

Constructor Details

#initialize(io) ⇒ Lexer

Returns a new instance of Lexer.



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# File 'lib/lexer.rb', line 33

def initialize io
  @ss = StringScanner.new io.read
end

Instance Method Details

#next_token ⇒ Object 



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# File 'lib/lexer.rb', line 37

def next_token
  return if @ss.eos?

  result = false
  while !result
    result = case
      when text = @ss.scan(SPACE)       then #ignore whitespace

      # Operators
      when text = @ss.scan(GTEQ)        then [:GTEQ, text]
      when text = @ss.scan(LTEQ)        then [:LTEQ, text]
      when text = @ss.scan(NEQ)         then [:NEQ, text]
      when text = @ss.scan(GT)          then [:GT, text]
      when text = @ss.scan(LT)          then [:LT, text]
      when text = @ss.scan(EQ)          then [:EQ, text]
      when text = @ss.scan(PLUS)        then [:PLUS, text]
      when text = @ss.scan(MATCH_OP)    then [:MATCH_OP, text]
      when text = @ss.scan(AND)         then [:AND, text]

      # SQL Keywords
      when text = @ss.scan(CHECK)       then [:CHECK, text]
      when text = @ss.scan(UNIQUE)      then [:UNIQUE, text]
      when text = @ss.scan(PRIMARY_KEY) then [:PRIMARY_KEY, text]
      when text = @ss.scan(FOREIGN_KEY) then [:FOREIGN_KEY, text]
      when text = @ss.scan(REFERENCES)  then [:REFERENCES, text]
      when text = @ss.scan(DELETE)      then [:DELETE, text]
      when text = @ss.scan(ON)          then [:ON, text]
      when text = @ss.scan(RESTRICT)    then [:RESTRICT, text]
      when text = @ss.scan(CASCADE)     then [:CASCADE, text]

      # Values
      when text = @ss.scan(IDENT)       then [:IDENT, text]
      when text = @ss.scan(STRLIT)      then [:STRLIT, text]
      when text = @ss.scan(INT)         then [:INT, text]

      # Syntax
      when text = @ss.scan(LPAREN)      then [:LPAREN, text]
      when text = @ss.scan(RPAREN)      then [:RPAREN, text]
      when text = @ss.scan(TYPE)        then [:TYPE, text]
      when text = @ss.scan(COMMA)       then [:COMMA, text]
      else
        x = @ss.getch
        [x, x]
    end
  end
  result
end

#tokenize ⇒ Object 



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# File 'lib/lexer.rb', line 85

def tokenize
  out = []
  while (tok = next_token)
    out << tok
  end
  out
end