Matlab与Python中yield关键字的等效项是什么? [英] What is the Matlab equivalent of the yield keyword in Python?

问题描述

我需要一次生成多个结果，而不是一次生成所有结果.

I need to generate multiple results but one at a time, as opposed to everything at once in an array.

我如何在Matlab中使用像Python这样的语法生成器来做到这一点?

How do I do that in Matlab with a generator like syntax as in Python?

推荐答案

在执行使用yield关键字的函数时，它们实际上返回一个生成器.生成器是迭代器的一种.尽管MATLAB都不提供语法，但是您可以自己实现迭代器接口" .这是类似于python中的xrange函数的示例:

When executing functions that use the yield keyword, they actually return a generator. Generators are a type of iterators. While MATLAB does not provide the syntax for either, you can implement the "iterator interface" yourself. Here is an example similar to xrange function in python:

classdef rangeIterator < handle
    properties (Access = private)
        i
        n
    end

    methods
        function obj = rangeIterator(n)
            obj.i = 0;
            obj.n = n;
        end

        function val = next(obj)
            if obj.i < obj.n
                val = obj.i;
                obj.i = obj.i + 1;
            else
                error('Iterator:StopIteration', 'Stop iteration')
            end
        end

        function reset(obj)
            obj.i = 0;
        end
    end
end

这是我们使用迭代器的方式:

Here is how we use the iterator:

r = rangeIterator(10);
try
    % keep call next() method until it throws StopIteration
    while true
        x = r.next();
        disp(x);
    end
catch ME
    % if it is not the "stop iteration" exception, rethrow it as an error
    if ~strcmp(ME.identifier,'Iterator:StopIteration')
        rethrow(ME);
    end
end

请注意，当在Python中的迭代器上使用构造for .. in ..时，它在内部会执行类似的操作.

Note the when using the construct for .. in .. in Python on iterators, it internally does a similar thing.

通过使用persistent变量或闭包来存储函数的局部状态，您可以使用常规函数而不是类编写类似的内容，并在每次调用时返回中间结果".

You could write something similar using regular functions instead of classes, by using either persistent variables or a closure to store the local state of the function, and return "intermediate results" each time it is called.

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