FUNCTION: LieTools/gActionVerma
USAGE: gActionVerma(X,upoly,hw); gActionVerma(i,upoly,hw);
SYNOPSIS: gActionVerma(X,pexpr,hw) will calculate the action of an element
  X of g on a Verma weight vector of the form upoly*|hw>. It
  returns the corresponding element of U[n_{-}].
  gActionVerma(i,pexpr,hw), where the first argument is an integer, returns
  gActionVerma(g[i],pexpr,hw). 
CAVEATS: requires a previously initialized global Lie algebra environment.
  (See LieTools[gSetup].)
EXAMPLE: 
> LieTools[gSetup](G,2);
Setting up Gtype = G   rnk = 2
> LieTools[gActionVerma](9,u(g[1],g[2]),[-1/2,-1/2]);

                            -u(g[1], g[3])

> LieTools[gActionVerma](g[14],u(g[1],g[2]),[-1/2,-1/2]);

                             -5/2 u(g[2])

> LieTools[gActionVerma](g[7]+g[8],u(g[1],g[2]),[-1/2,-1/2]);

                           -4 u(g[1], g[2])

SEE ALSO: LieTools[EvalOnHW], LieTools[VermaNorm]
