Question

我正在

syntax error before: 'end'

我每次都为分配运行此代码：

closest(_P, _PointList) -> 
    case (length(_PointList =:= 0)) of 
        true -> {0,0};
        false -> closest(_P, tl(_PointList), distance(_P, hd(_PointList)), 1)
    end.
    % Llength = length(_P),

closest(P, _PointList, _Distance, _Index) -> 
    case (length(_PointList =:= 0)) of 
        true -> {_Index, _Distance};
        false -> 
            New_Distance = min(_Distance, distance(_P, hd(_PointList)),
            case (New_Distance < _Distance) of 
                true -> closest(_P, tl(_PointList), New_Distance, _Index + 1);
                false -> closest(_P, tl(_PointList), _Distance, _Index)
            end
    end
end.

有人可以帮我弄清楚为什么会这样吗？感谢

Answer 1

错过了)的{{1}}并且有额外的min/2

应该是：

end

Answer 2

你可能想写这个：

closest(_P, []) -> {0, 0};
closest(P, [H|T]) ->
    closest(P, T, distance(P, H), 0, 1).

closest(_P, [], Distance, ClosestIndex, _Index) ->
    {ClosestIndex, Distance};
closest(P, [H|T], Distance, ClosestIndex, Index) ->
    case distance(P, H) of
        New_Distance when New_Distance < Distance ->
            closest(P, T, New_Distance, Index, Index + 1);
        _ ->
            closest(P, T, Distance, ClosestIndex, Index + 1)
    end.

Answer 3

这看起来很可疑

case (length(_PointList =:= 0)) of

应该是

case length(_PointList) =:= 0 of

此外，您应该获得发现错误（或附近）的行号。错误堆栈跟踪肯定有帮助。

语法错误之前：＆＃39;结束＆＃39;在编译代码时

3 个答案: