Package transf :: Module transformation :: Class Transformation

Class Transformation

Abstract class for term transformations.

A transformation takes as input a term and returns the transformed term, or raises a failure exception if it is not applicable. It also receives a transformation context to which it can read/write.

A transformation should not maintain any state itself, i.e., different calls to the apply method with the same term and context must produce the same result.

Instance Methods

__init__(self)
Constructor.

__call__(self, trm, **kargs)
User-friendly wrapper for apply.

apply(self, trm, ctx)
Applies the transformation to the given term with the specified context.

__neg__(self)
Negation operator.

__pos__(self)
Positive operator.

__add__(self, other)
Addition operator.

__mul__(self, other)
Multiplication operator.

__pow__(self, other)
Exponentiation operater.

__repr__(self)
repr(x)

Inherited from object: __delattr__, __getattribute__, __hash__, __new__, __reduce__, __reduce_ex__, __setattr__, __str__

Properties
Inherited from `object`: `__class__`

Method Details

init(self)
(Constructor)

Constructor.

Overrides: object.__init__

apply(self, trm, ctx)

Applies the transformation to the given term with the specified context.

Parameters:

trm - Term to be transformed.
ctx - Transformation context.

Returns:

The transformed term on success.

Raises:

exception.Failure - on failure.

neg(self)

Negation operator. Shorthand for lib.combine.Not

pos(self)

Positive operator. Shorthand for lib.combine.Try

add(self, other)
(Addition operator)

Addition operator. Shorthand for lib.combine.Choice

mul(self, other)

Multiplication operator. Shorthand for lib.combine.Composition

pow(self, other)

Exponentiation operater. Shorthand for lib.combine.GuardedChoice.

For example, t1 **t2** t3 is equivalent, to lib.combine.GuardedChoice(t1, t2, t3). The exponentiation operator is right associative, so t1 **t2** t3 **t4** t5 is the same as t1 **t2** (t3 **t4** t5). However note that its precedence is higher than other operators, therefore parenthesis must be used around them.

See Also: http://docs.python.org/ref/summary.html for a summary of Python's operators precedence.

repr(self)
(Representation operator)

repr(x)

Overrides: object.__repr__: (inherited documentation)

Class Transformation

__init__(self) (Constructor)

apply(self, trm, ctx)

__neg__(self)

__pos__(self)

__add__(self, other) (Addition operator)

__mul__(self, other)

__pow__(self, other)

__repr__(self) (Representation operator)