FUNCTION:  IrrChars - irreducible characters of a Coxeter group,    
CALLING SEQUENCE:  IrrChars(R);,    
PARAMETERS:  R = a root system data Structure,SYNOPSIS:   
  A character of W(R) is represented as a list of values [a_1,...,a_l],
  where a_i is the value of the character on an element in the i-th
  conjugacy class of W(R). The ordering of the conjugacy classes is the
  same as the ordering used by the functions ClassRep, ClassSize, Cprod,
  PermChar, Induce, and Restrict. In particular, the degree of the
  character is the first value listed. 
  IrrChars(R) returns the list of irreducible characters of W(R).
  The characters of the exceptional groups E-F-H are read from prestored
  tables in the Coxeter/lib directory. The characters for the remaining
  irreducible groups are generated "on demand".
  The characters of the group A.(n-1) are listed in the same order as in
  combinat[character](n):  the corresponding sequence of partitions
  Indexing the characters is the reverse of combinat[partition](n).
  The character values of the non-crystallographic groups H3 and H4 are
  stored as expressions of the form  a + b * sqrt(5), where a and b are
  rational. Arithmetic operations involving these expressions are not
  automatically simplified by Maple, but can be simplified through the use
  of the expand and rationalize functions. The non-integer character values
  of the groups I2[m] are generated as expressions of the form  2*cos(a*Pi)
  where a is rational. For certain values of a these expressions are subject
  to automatic simplification by Maple as radical expressions.
  For a description of root system data Structures, see Coxeter[Structure].
EXAMPLES:   
  IrrChars(A2);                    yields   [[1,1,1], [2,0,-1], [1,-1,1]]
  [seq(f[1],f=IrrChars(H3))];      yields       [1,1,3,3,3,3,4,4,5,5],    
           Cprod, PermChar, Induce, Restrict, Structure):
