FUNCTION: IsDiagonal - test whether the argument is a diagonal coding of a partition

CALLING SEQUENCE:

IsDiagonal(expr)

TYP[IsDiagonal](expr)

PARAMETERS:

expr = any expression

SYNOPSIS:

• The IsDiagonal function tests whether expr denotes a coding of all diagonals of a partition. The argument expr must be a list of two components [dl, o] where dl is a list of diagonals and o the integer denoting the position of the main diagonal of the diagram of the partition.

• Whenever there is a conflict between the function name IsDiagonal and another name used in the same session, use the long form TYP['IsDiagonal'].

EXAMPLES:

> with(TYP):
> IsDiagonal([[1, 2, 2, 1, 1, 1], 3]);
 
                                     true