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HELP FOR: grDalias
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CALLING SEQUENCE:  grDalias ( function, coord1, str1, coord2, str2..)
                   grDalias ( function1, function2, ..., coord1, str1, ...)

      PARAMETERS:  function - name of a function which appears in a metric
                   coord    - name of a coordinate
                   str      - string to denote differentiation with respect
                              to coord1

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SYNOPSIS:

- Creates aliases for MapleV output of derivatives of functional
  dependencies allowing them to be replaced by user specified characters,
  in order to simplify the appearance of output.

- The grDalias() command generates alias statements so e.g.  D[1](f)(x,y,z)
  or diff(f(x,y,z),x) appears as f' if the string associated with x is '.

           d 
   ie.    -- f(x,y,z)  would be represented as  f'.
          dx

- grDalias() can be applied either at any time during a set of calculations.
  All components displayed after the alias assignment will make use of the
  aliases.

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EXAMPLES:

# Consider RiemSq (the Kretschmann scalar) for the Robertson Walker metric.
# With the use of grDalais the output can be presented in a more
# readable form denoting differentiation by using an apostrophe

> qload ( rw ):
> grcalc ( RiemSq ):
> grdisplay ( _ ):
 
                             For the rw spacetime:
 
                          Full Contraction of Riemann
 
                                                      /   2      \2
                2       /  d      \2   /  d      \4   |  d       |      2
               k  + 2 k |---- a(t)|  + |---- a(t)|  + |----- a(t)|  a(t)
                        \ dt      /    \ dt      /    |   2      |
                                                      \ dt       /
       K  = 12 ----------------------------------------------------------
                                              4
                                          a(t)
 
> grDalias ( a(t), t, `'` ):
Aliases created

> grdisplay ( RiemSq ):
                              For the rw metric.

                          Full contraction of Riemann

                                     2     2    2         2     4
                                  a''  a(t)  + k  + 2 k a'  + a'
                          K  = 12 -------------------------------
                                                   4
                                               a(t)

# similarly for the Bondi metric. The following example replaces
# r-derivatives by an apostrophe (') and v-derivatives by a hat (^).

> qload ( bondi ):
> grcalc ( G(dn,up) ):

> grDalias ( c(r,v), m(r,v), v, `^`, r, `'`):
Aliases created

> grdisplay ( G(dn,up) ):
                             For the bondi metric.

                  Mixed Einstein (second index contravariant)

                        r     c' r - 2 c' m(r,v) - c(r,v) m'
                   G  r   = 2 --------------------------------
                                          2
                                         r  c(r,v)

                                   v         c'
                              G  r   = 2 ----------
                                                2
                                         c(r,v) r

                                    .
                                    .
                                    .
                                   etc.

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SEE ALSO: autoAlias, diffAlias.
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