Package com.singularsys.jep.configurableparser

Class ShuntingYard

java.lang.Object
com.singularsys.jep.configurableparser.ShuntingYard
All Implemented Interfaces:
GrammarParser
Direct Known Subclasses:
LineNumberingShuntingYard
public class ShuntingYard extends Object implements GrammarParser
An operator precedence parser based on the shunting yard algorithm.

  • Field Details

  • Constructor Details

    • ShuntingYard

      public ShuntingYard(Jep jep, List<GrammarMatcher> gm)
      Normal constructor, iterator set in parse(Iterator)
      Parameters:
      jep - Jep instance
      gm - list of grammar rules

  • Method Details

    • parse

      public Node parse(Iterator<Token> input) throws ParseException
      Main entry point, construct tree from sequence of tokens.
      Specified by:
      parse in interface GrammarParser
      Parameters:
      input - stream of tokens
      Returns:
      constructed tree
      Throws:
      ParseException - if the input cannot be parsed

    • parseSubExpression

      public Node parseSubExpression() throws ParseException
      Callback function used by GrammarMatchers
      Specified by:
      parseSubExpression in interface GrammarParser
      Returns:
      node tree
      Throws:
      ParseException - if the input cannot be parsed

    • expression

      protected void expression() throws ParseException
      Match prefixSuffix() optionally followed by a binary or ternary operator or an implicit multiplication. Consumes tokens and pushes operators found onto to the stack.
      Throws:
      ParseException

    • parsePrefixSuffix

      public Node parsePrefixSuffix() throws ParseException
      Callback function used by GrammarMatchers where the matcher expects a simple number, variable, or function call with optional, prefix or suffix operator.
      Specified by:
      parsePrefixSuffix in interface GrammarParser
      Returns:
      node tree or null if parsing failed to match
      Throws:
      ParseException - if the input cannot be parsed

    • prefixSuffix

      protected void prefixSuffix() throws ParseException
      A prefix() optionally followed by suffix operators.
      Throws:
      ParseException

    • prefixSuffixUnchecked

      protected ShuntingYard.PrefixRes prefixSuffixUnchecked() throws ParseException
      Attempt to match a prefix optionally followed by suffix operators.
      Returns:
      code indicating state of parsing
      Throws:
      ParseException - if node construction fails
      Since:
      3.5

    • prefixUnchecked

      protected ShuntingYard.PrefixRes prefixUnchecked() throws ParseException
      Matches identifies, numbers, prefix operators and plugged in grammar matchers.
      Returns:
      code indicating state of parsing
      Throws:
      ParseException - if node construction fails
      Since:
      3.5

    • prefix

      protected void prefix() throws ParseException
      Matches identifies, numbers, prefix operators and plugged in grammar matchers. Wrapper function around the prefixUnchecked()
      Throws:
      ParseException - if input fails to match or error construction node tree

    • pushOp

      protected void pushOp(Operator op, Token tok) throws ParseException
      The pushOp function is worth some explanation Say 1+2*3 is parsed. First + is pushed onto the stack, then * is pushed. For 1*2+3. * is pushed, when + is encountered * has tighter precedence so it and the top two elements from the node stack are popped, the result computed and pushed on the node stack. Special cases -1+2 [uminus,+],[1] -> [+],[-1] -> [+],[-1,2] -> [],[(-1)+2] -1^2 [uminus,^],[1] -> [uminus,^],[1] -> [uminus,^],[1,2] -> [uminus],[1^2] -> [],[-(1^2)] 1^-2 [^],[1] -> [^,uminus],[1] ->[^,uminus],[1,2] -> [^],[1,(-2)] ->[],[1^(-2)]
      Parameters:
      op -
      tok - Token operator came from
      Throws:
      ParseException

    • compareOps

      protected boolean compareOps(Operator op1, Operator op2)
      Compare operators based on their precedence and associativity.
      Parameters:
      op1 -
      op2 -
      Returns:
      true if op1 has a lower precedence than op2, or equal precedence and a left assoc op, etc.

    • popOp

      protected void popOp() throws ParseException
      Pops an operator off the Operator stack, and creates a new node. The children of the node are popped off the node stack and the result is pushed onto the node stack.
      Throws:
      ParseException

    • dumpState

      protected void dumpState(String msg)

    • getIterator

      public Lookahead2Iterator<Token> getIterator()

    • setIterator

      public void setIterator(Lookahead2Iterator<Token> it)
      Description copied from interface: GrammarParser
      Set the iterator used by the GrammarParser.parseSubExpression()
      Specified by:
      setIterator in interface GrammarParser
      Parameters:
      it - the iterator