Package rxpy :: Package graph :: Module opcode :: Class Lookahead

Class Lookahead

Lookahead match (one that does not consume any input).

equal is True if the lookahead should succeed for the match to continue and False if the lookahead should fail.
forwards is True if the lookahead should start from the current position and False if it should end there.
next contains two values. next[1] is the lookahead expression; next[0] is the continuation of the normal match on success.

For lookbacks (forwards is False) the expression has a postfix of "$" so that direct searching (not matching) of the string up to the current point provides the to check. Engines are welcome to use more efficient approaches, as long as the results remain correct.

Instance Methods

[hide private]

__init__(self, equal, forwards)
Subclasses should pay attention to the relationship between constructor kargs and attributes assumed in .clone. source code

__str__(self)
Subclasses must implement something useful here, which will be displayed in the graphviz node (see repr).

source code

visit(self, visitor, state=None)
The visitor pattern - used to evaluate the graph by an interpreter, for example.

source code

Inherited from support.BaseSplitNode: concatenate

Inherited from support.BaseNode: __repr__, clone, consumer, deep_eq, size, start

Inherited from support.BaseNode (private): _kargs, _node_eq

Inherited from object: __delattr__, __format__, __getattribute__, __hash__, __new__, __reduce__, __reduce_ex__, __setattr__, __sizeof__, __subclasshook__

Properties

[hide private]

Inherited from object: __class__

Method Details

[hide private]

init(self, equal, forwards)
(Constructor)

source code

Subclasses should pay attention to the relationship between constructor kargs and attributes assumed in .clone.

Overrides: object.__init__: (inherited documentation)

str(self)
(Informal representation operator)

source code

Subclasses must implement something useful here, which will be displayed in the graphviz node (see repr).

Overrides: object.__str__: (inherited documentation)

visit(self, visitor, state=None)

source code

The visitor pattern - used to evaluate the graph by an interpreter, for example. Calls back to the visitor via the interface described in rxpy.parser.visitor.Visitor.

Overrides: support.BaseNode.visit: (inherited documentation)

Class Lookahead

__init__(self, equal, forwards) (Constructor)

__str__(self) (Informal representation operator)

visit(self, visitor, state=None)

init(self, equal, forwards)
(Constructor)

str(self)
(Informal representation operator)