CanonPrint.html

Function: Canon[CanonPrint, CanonUnPrint] - printing routines for the Canon package

Calling Sequence:
CanonPrint(tensor);

CanonUnPrint(printed tensor);

Parameters:
tensor - a tensor expression

printed tensor - a tensor expression as printed by CanonPrint

CanonPrint and CanonUnPrint provide the interface for printing tensor expressions on the screen.

CanonPrint recognizes covariant and contravariant indices, products, sums and equalities. Notice that it is only a printing routine, so free indices on both sides of equations are not checked. Internally, the product, sum or equality is broken down into single tensors and the internal procedure `print/_TENSOR` prints each of them, formally treating the indexed objects as products of the indices.

CanonUnPrint receives as input a tensor expression as CanonPrint would output it, or equivalently an expression with the tensors written as _TENSOR calls. It is used to convert from the print friendly tensors to the internal format used for indicial manipulations.

Examples:

> with(Canon):

> CanonPrint(T[a,-b]);

> CanonPrint(T[a,-b]*R[b,-c]);

The following commands reveal some of the internal structure:

> lprint(CanonPrint(T[a,-b]));

_TENSOR(T[a,-b])

> CanonUnPrint(%);

> CanonUnPrint( _TENSOR(T[a,-b])*_TENSOR(R[b,-c]) );

The user may employ the function _SCALAR for powering of an expression with no free indices. This function has also an associated `print/_SCALAR` procedure.

> CanonPrint(_SCALAR(V[a]*V[-a])^2);

> lprint(%);

_SCALAR(_TENSOR(V[a])*_TENSOR(V[-a]))^2

See Also: CanonDefine , Canonical , CanonicalOne