NAME
        ParseIX -- initialize an input expression given a description string.
                   (V36)

   SYNOPSIS
        failureCode = ParseIX(description,ix);
        D0                    A0          A1

        long parseix(strptr,ix *);

   FUNCTION
        Given an input description string and an allocated input
        expression, sets the fields of the input expression to
        correspond to the description string.

   INPUTS
        description - the string to parse
        ix - the input expression to hold the result of the parse

   RESULTS
        failureCode -  0 if all went well,
                      -1 if tokens after end (code spec)
                      -2 if 'description' was NULL

   SEE ALSO
        <libraries/commodities.h>, matchix()