ifthen

           This function returns a certain value if the expression is
           true, otherwise the other value. This function can be used
           as an "if statement in an expression" like the C ?: -
           operator.
           Other than the if statement this function works for arrays
           also provided the dimensions of  expression and true/false
           values are the same.

           Misc.

           val = ifthen(expression,trueval[,falseval])

           expression - boolean expression. For all elements which
                        are true the trueval element will be
                        returned, otherwise the falseval
           trueval    - Value or array to be returned when the
                        expression is logical true ( not zero).
           falseval   - (optional) Value or array to be returned when
                        the exression is logical false (zero). If
                        this value is not given 0 will be returned.

           Returns val = trueval for those elements whose expression
           is not 0, otherwise the corresponding falseval element.

           But no!

           None.

           Expression should be boolean. If not falseval is given the
           trueval type must be either float or integer value.

          y = sqrt(ifthen(x ge 0,x)) -> get square root for valid
              values only.

          $Log: ifthen.pro,v $
          Revision 1.1  2003/12/30 07:27:09  goehler
          function to  perform scalar/array boolean expression evaluation returning
          alternative values

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