esys.escript.util.Symbol

Package esys :: Package escript :: Module util :: Class Symbol

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Type Symbol

object --+
         |
        Symbol

Known Subclasses:: DependendSymbol

Symbol class.

Symbol class objects provide the same functionality as numarray.NumArray and escript.Data objects but they do not have a value and therefore cannot be plotted or visualize. The main purpose is the possibilty calculate derivatives with respect to other Symbols used to define a Symbol.

Method Summary
	`__init__(self, shape, args, dim)` Creates an instance of a symbol of a given shape.
	`__abs__(self)` returns a S{Symbol} representing the absolute value of the object.
	`__add__(self, other)` add another object to this object @param other: object to be added to this object @type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
	`__div__(self, other)` divides this object by other object @param other: object dividing this object @type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
	`__getitem__(self, index)` returns the slice defined by index...
	`__mul__(self, other)` multiplies this object with other object @param other: object to be mutiplied by this object @type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
	`__neg__(self)` returns -self.
	`__pos__(self)` returns +self.
	`__pow__(self, other)` raises this object to the power of other @param other: exponent @type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
	`__radd__(self, other)` add this object to another object @param other: object this object is added to @type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
	`__rdiv__(self, other)` divides this object by other object @param other: object dividing this object @type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
	`__rmul__(self, other)` multiplies this object with other object @param other: object this object is multiplied with @type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
	`__rpow__(self, other)` raises an object to the power of this object @param other: basis @type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
	`__rsub__(self, other)` subtracts this object from another object @param other: object this object is been subtracted from @type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
`str`	`__str__(self)` a string representation of the symbol.
	`__sub__(self, other)` subtracts another object from this object @param other: object to be subtracted from this object @type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
typically `escript.Symbol` but other types such as `float`, `escript.Data`, `numarray.NumArray` are possible.	`diff(self, arg)` returns the derivative of the symbol with respect to `Symbol` arg
a single object or a list of objects	`getArgument(self, i)` returns the i-th argument of the symbol
`list` of objects	`getDifferentiatedArguments(self, arg)` applifies differentials to the arguments of this object and returns the result as a list.
`int` if the dimension is defined. Otherwise `None` is returned.	`getDim(self)` the spatial dimension
`str`	`getMyCode(self, argstrs, format)` returns a program code that can be used to evaluate the symbol.
`int`	`getRank(self)` the rank of the symbol
`tuple` of `int`	`getShape(self)` the shape of the symbol.
`list` of objects	`getSubstitutedArguments(self, argvals)` substitutes symbols in the arguments of this object and returns the result as a list.
`bool`	`isAppropriateValue(self, arg)` checks if the given argument arg can be used as a substitution of this object.
`escript.Symbol`, `float`, `escript.Data`, `numarray.NumArray` depending on the degree of substitution	`substitute(self, argvals)` assigns new values to symbols in the definition of the symbol.
Inherited from object
	`__delattr__(...)` x.__delattr__('name') <==> del x.name
	`__getattribute__(...)` x.__getattribute__('name') <==> x.name
	`__hash__(x)` x.__hash__() <==> hash(x)
	`__new__(T, S, ...)` T.__new__(S, ...) -> a new object with type S, a subtype of T
	`__reduce__(...)` helper for pickle
	`__reduce_ex__(...)` helper for pickle
	`__repr__(x)` x.__repr__() <==> repr(x)
	`__setattr__(...)` x.__setattr__('name', value) <==> x.name = value

Method Details

init(self, shape=(), args=[], dim=None)
(Constructor)

Creates an instance of a symbol of a given shape. The symbol may depending on a list of arguments args which may be symbols or any other object.

Parameters:: shape - the shape
(type=tuple of int); dim - spatial dimension of the symbol. If dim=None the spatial dimension is undefined.
(type=None or int)

Overrides:: __builtin__.object.__init__

abs(self)

returns a S{Symbol} representing the absolute value of the object.

add(self, other)
(Addition operator)

add another object to this object

@param other: object to be added to this object
@type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
@return:  a S{Symbol} representing the sum of this object and C{other}
@rtype: L{DependendSymbol}

div(self, other)

divides this object by other object

@param other: object dividing this object
@type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
@return: a S{Symbol} representing the quotient of this object and C{other}
@rtype: L{DependendSymbol}

getitem(self, index)
(Indexing operator)

returns the slice defined by index

@param index: defines a 
@type index: C{slice} or C{int} or a C{tuple} of them
@return: a S{Symbol} representing the slice defined by index
@rtype: L{DependendSymbol}

mul(self, other)

multiplies this object with other object

@param other: object to be mutiplied by this object
@type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
@return: a S{Symbol} representing the product of the object and C{other}.
@rtype: L{DependendSymbol} or 0 if other is identical to zero.

neg(self)

returns -self.

@return:  a S{Symbol} representing the negative of the object
@rtype: L{DependendSymbol}

pos(self)

returns +self.

@return:  a S{Symbol} representing the positive of the object
@rtype: L{DependendSymbol}

pow(self, other)

raises this object to the power of other

@param other: exponent
@type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
@return: a S{Symbol} representing the power of this object to C{other}
@rtype: L{DependendSymbol} or 1 if C{other} is identical to zero.

radd(self, other)
(Right-side addition operator)

add this object to another object

@param other: object this object is added to
@type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
@return: a S{Symbol} representing the sum of C{other} and this object object
@rtype: L{DependendSymbol}

rdiv(self, other)

divides this object by other object

@param other: object dividing this object
@type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
@return: a S{Symbol} representing the quotient of C{other} and this object
@rtype: L{DependendSymbol} or 0 if C{other} is identical to zero.

rmul(self, other)

multiplies this object with other object

@param other: object this object is multiplied with
@type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
@return: a S{Symbol} representing the product of C{other} and the object.
@rtype: L{DependendSymbol} or 0 if other is identical to zero.

rpow(self, other)

raises an object to the power of this object

@param other: basis 
@type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
@return: a S{Symbol} representing the power of C{other} to this object
@rtype: L{DependendSymbol} or 0 if C{other} is identical to zero.

rsub(self, other)

subtracts this object from another object

@param other: object this object is been subtracted from
@type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
@return: a S{Symbol} representing the difference of this object and C{other}.
@rtype: L{DependendSymbol}

str(self)
(Informal representation operator)

a string representation of the symbol.

Returns:: a string representation of the object
(type=str)

Overrides:: __builtin__.object.__str__

sub(self, other)
(Subtraction operator)

subtracts another object from this object

@param other: object to be subtracted from this object
@type other: L{escript.Symbol}, C{float}, L{escript.Data}, L{numarray.NumArray}.
@return: a S{Symbol} representing the difference of C{other} and this object 
@rtype: L{DependendSymbol}

diff(self, arg)

returns the derivative of the symbol with respect to Symbol arg

Parameters:: arg - the derivative is calculated with respect to arg
(type=typically escript.Symbol but can also be float, escript.Data, numarray.NumArray depending the involved functions and data.)

Returns:: derivative with respect to arg
(type=typically escript.Symbol but other types such as float, escript.Data, numarray.NumArray are possible.)

Note: this method is overwritten by a particular Symbol

getArgument(self, i=None)

returns the i-th argument of the symbol

Parameters:: i - index of the argument requested.
(type=int or None)

Returns:: the vlaue of the i-th argument or i is not specified the list of all arguments.
(type=a single object or a list of objects)

Raises:: IndexError - if the requested index does not exist

getDifferentiatedArguments(self, arg)

applifies differentials to the arguments of this object and returns the result as a list.

Parameters:: arg - the derivative is calculated with respect to arg
(type=typically escript.Symbol but can also be float, escript.Data, numarray.NumArray depending the involved functions and data.)

Returns:: list of object obtained by calculating the derivatives of the argumenst with respct to arg
(type=list of objects)

getDim(self)

the spatial dimension

@return : the spatial dimension

Returns:: int if the dimension is defined. Otherwise None is returned.

getMyCode(self, argstrs, format='escript')

returns a program code that can be used to evaluate the symbol.

Parameters:: argstrs - gives for each argument a string representing the argument for the evaluation.
(type=list of str.); format - specifies the format to be used. At the moment only "escript", "str" and "text" are supported.
(type=str)

Returns:: a piece of program code which can be used to evaluate the expression assuming the values for the arguments are available.
(type=str)

Raises:: NotImplementedError - if no implementation for the given format is available

Note: This method has to be overwritten by subclasses.

getRank(self)

the rank of the symbol

Returns:: the rank of the symbol. This is length of the shape
(type=int)

getShape(self)

the shape of the symbol.

@return : the shape of the symbol.

Returns:: tuple of int

getSubstitutedArguments(self, argvals)

substitutes symbols in the arguments of this object and returns the result as a list.

Parameters:: argvals - Symbols and their substitutes. The Symbol u in the expression defining this object is replaced by argvals[u].
(type=dict with keywords of type Symbol.)

Returns:: list of the object assigned to the arguments through substitution or for the arguments which are not Symbols the value assigned to the argument at instantiation.
(type=list of objects)

isAppropriateValue(self, arg)

checks if the given argument arg can be used as a substitution of this object. The method checks the shape of arg and, if the spatial dimension is defined, the spatial dimension of arg.

Parameters:: arg - a given object
(type=
numarray.NumArray,escript.Data,float, int, Symbol)

Returns:: True if arg is a suitbale object to be used for substitution. Otherwise False is returned.
(type=bool)

substitute(self, argvals)

assigns new values to symbols in the definition of the symbol. The method replaces the Symbol u by argvals[u] in the expression defining this object.

Parameters:: argvals - new values assigned to symbols
(type=dict with keywords of type Symbol.)

Returns:: result of the substitution process. Operations are executed as much as possible.
(type=escript.Symbol, float, escript.Data, numarray.NumArray depending on the degree of substitution)

Raises:: NotImplementedError - if no implementation for the given format is available; TypeError - if a value for a Symbol cannot be substituted.

Note: this method has to be overwritten by a particular Symbol

Generated by Epydoc 2.1 on Thu Apr 27 11:16:24 2006

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Type Symbol

__init__(self, shape=(), args=[], dim=None) (Constructor)

__abs__(self)

__add__(self, other) (Addition operator)

__div__(self, other)

__getitem__(self, index) (Indexing operator)

__mul__(self, other)

__neg__(self)

__pos__(self)

__pow__(self, other)

__radd__(self, other) (Right-side addition operator)

__rdiv__(self, other)

__rmul__(self, other)

__rpow__(self, other)

__rsub__(self, other)

__str__(self) (Informal representation operator)

__sub__(self, other) (Subtraction operator)