Package org.parboiled.support

Class Var<T>

  • Type Parameters:
    T - the type wrapped by this Var
    Direct Known Subclasses:
    StringBuilderVar, StringVar
    public class Var<T>
extends Reference<T>

    This class provides a "local variable"-like construct for action expressions in parser rule methods. Var objects wrap an internal value of an arbitrary (reference) type, can have an initial value, allow read/write access to their values and can be passed around as parameters to nested rule methods. Each rule invocation (i.e. rule matching attempt) receives its own Var scope (which is automatically initialized with the initial value), so actions in recursive rules work just like expected.

    Var objects generally behave just like local variables with one exception:
    When rule method A() passes a Var defined in its scope to another rule method B() as a parameter and an action in rule method B() writes to this Var all actions in rule method A() running after B() will "see" this newly written value (since values in Var objects are passed by reference)

    • Constructor Detail

      • Var

        public Var()
        Initializes a new Var with a null initial value.

      • Var

        public Var​(T value)
        Initializes a new Var with the given initial value.
        Parameters:
        value - the value

      • Var

        public Var​(Factory<T> initialValueFactory)
        Initializes a new Var. The given factory will be used to create the initial value for each "execution frame" of the enclosing rule.
        Parameters:
        initialValueFactory - the factory used to create the initial value for a rule execution frame

    • Method Detail

      • getName

        public String getName()
        Gets the name of this Var.
        Returns:
        the name

      • setName

        public void setName​(String name)
        Sets the name of this Var.
        Parameters:
        name - the name

      • getLevel

        public int getLevel()
        Returns the current frame level of this variable, the very first level corresponding to zero.
        Returns:
        the current level

      • enterFrame

        public boolean enterFrame()
        Provides a new frame for the variable. Potentially existing previous frames are saved. Normally you do not have to call this method manually as parboiled provides for automatic Var frame management.
        Returns:
        true

      • exitFrame

        public boolean exitFrame()
        Exits a frame previously entered with enterFrame(). Normally you do not have to call this method manually as parboiled provides for automatic Var frame management.
        Returns:
        true