Parses a query expression command string and sets up a query
    context if the command is syntactically correct.

    Format

      SCA$QUERY_PARSE  query_context, query_expression_string

                       [,query_expression_length]

1  –  Arguments

 query_context
    type:       $SCA_QUERY_CONTEXT
    access:     read/write
    mechanism:  by reference

    An SCA query context that is to describe the indicated query
    expression.

 query_expression_string
    type:       character string
    access:     read only
    mechanism:  by descriptor

    A query expression string.

 query_expression_length
    type:       longword
    access:     write only
    mechanism:  by reference

    Optional. Length of the query expression, returned from the
    parser.

2  –  Condition Values Returned

    SCA$_NORMAL           The query expression string has been
                          successfully parsed.

    SCA$_MORETEXT         Warning. The query expression string has
                          been successfully parsed, but the text
                          following the query expression is not a
                          legal part of the query expression. This
                          condition is returned only if the query_
                          expression_length parameter is specified. If
                          the query_expression_length parmeter is not
                          specified, then this routine insists that
                          the whole query_expression_string argument
                          be a legal query expression; in this case
                          all errors are signaled.

3  –  Description

    The SCA$QUERY_PARSE routine parses a query expression string and
    sets up a query context if the command is syntactically correct.

    This routine will become obsolete in a future version of SCA.