xget(+Handle, +Index, -Value)

Handle

An external data handle.

Index

An integer.

Value

A variable.

Description

The xget/3 predicate invokes one of the methods, the get-method. The intended meaning is that it gets a field of the external data structure (indicated by Index) and unifies it with Value. The details of how the index is interpreted and how the field's value is converted to an ECLiPSe term is dependent on the get-method supplied by external code.

Modes and Determinism

• xget(+, +, -) is det

Exceptions

(4) instantiation fault

Handle or Index is uninstantiated.

(5) type error

Handle is not a handle, or Index is not an integer.

(6) out of range

Index is out of range (if check implemented by method).

(141) unimplemented functionality

The get-method is not implemented for this handle.

Examples

    /* C code with embedded ECLiPSe call, passing data via C ararys */
    #include "eclipse.h"

    #define N 5
    double data_in[N] = {1.1,2.2,3.3,4.4,5.5};
    double data_out[N];

    main()
    {
        pword   call;
        int     i;
        
        ec_init();
        ec_post_string("[my_code]");
        ec_post_goal(
            ec_term(ec_did("process", 3),
                ec_long(N),
                ec_handle(&ec_xt_double_arr, (t_ext_ptr) data_in),
                ec_handle(&ec_xt_double_arr, (t_ext_ptr) data_out)
            )
        );
        if (ec_resume() == PSUCCEED)
        {
            for (i=0; i<N; i++)
                printf("%f,", data_out[i]);
        }
        ec_cleanup();
    }


    /* ECLiPSe code in file my_code.pl */

    process(0, _, _) :- !.
    process(N, In, Out) :-
        N1 is N-1,
        xget(In, N1, X),
        Y is sqrt(X),
        xset(Out, N1, Y),
        process(N1, In, Out).


    /* Sample run */

    % main
    1.048809,1.483240,1.816590,2.097618,2.345208,

See Also