CPW-Engine_algebraic

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**[[Home]] * [[Engines]] * [[CPW-Engine]] * Algebraic**

=Description= 
When communicating with the [[GUI]], the Engine is supposed to use the [[Algebraic Chess Notation|algebraic game notation]]. The code on this page is used to translate the positions in the engine native form to the GUI friendly representation and back again.

The algebraic game notation first has 2 characters representing the square the piece comes from (eg.: "e2"). Then 2 characters to indicate the square the piece moves to (eg.: "e4"). And finally, in case of a promotion, the piece the pawn is promoted to ( q | r | b | n ). So a possible starting move for white could be "e2e4". And a possible promotion move could be "a7a8n".

=Code= 
==int convert_0x88_a(sq, a)== 
[[code format="cpp"]]
int convert_0x88_a(int sq, char * a) {
    a[0] = COL(sq) + 'a';
    a[1] = ROW(sq) + '1';
    a[2] = 0;
    return 0;
}
[[code]]

==int convert_a_0x88(a)== 
[[code format="cpp"]]
int convert_a_0x88(char * a) {
    int sq = 0;
    sq = a[0] - 'a';
    sq += (a[1] - '1') * 16;

    return sq;
}
[[code]]

==int algebraic_moves(a)== 
[[code format="cpp"]]
int algebraic_moves(char * a) {

    smoves m;

    while ((a[0] >= 'a') && (a[0] <= 'h')) {

        m.from = convert_a_0x88(a);
        m.to = convert_a_0x88(a+2);

        m.piece_from = b.pieces[m.from];
        m.piece_to = b.pieces[m.from];
        m.piece_cap = b.pieces[m.to];

        m.flags = 0;
        m.castle = 0;
        m.ep = 0;
        m.ply = 0;
        m.score = 0;

        switch (a[4]) {
        case 'q': m.piece_to = PIECE_QUEEN; a++; break;
        case 'r': m.piece_to = PIECE_ROOK; a++; break;
        case 'b': m.piece_to = PIECE_BISHOP; a++; break;
        case 'n': m.piece_to = PIECE_KNIGHT; a++; break;
        }

        //castling
        if ((m.piece_from == PIECE_KING) &&
            ((m.from == E1 && (m.to == G1 || m.to == C1)) ||
            (m.from == E8 && (m.to == G8 || m.to == C8)))) {
                m.flags = MFLAG_CASTLE;
        }

        /*ep
            if the moving-piece is a Pawn, the square it moves to is empty and
            it was a diagonal move it has to be an en-passant capture.
        */
        if ((m.piece_from == PIECE_PAWN) &&
            (m.piece_cap == PIECE_EMPTY) &&
            ((abs(m.from-m.to)==15)||(abs(m.from-m.to)==17))) {
                m.flags = MFLAG_EPCAPTURE;
        }

        move_make(m);

        a += 4;

        while (a[0]==' ') a++;

    }

    return 0;
}
[[code]]
=What links here?= 
[[include page="CPW-Engine_algebraic" component="backlinks" limit="20" ]]
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