Suppose you want to train somebody to do something and you want the training such that they'll keep on doing it even if you're not training them anymore, which is typically what you want.

假设你想训练某人做某事,你想要找到一种训练方法,使得他们即便不再接受训练,也依然能够持续展现某种行为，而这正是你想要的。

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but if you explain it to your friend that you or she should not have or should have done something,

如果你想要向你的朋友解释，或者她应该做某事的时候，

I should have 课堂 - SpeakingMax英语口语达人

It means that you wish or desire to do something.

表示你想要或期望做某事。

I want to 课堂 - SpeakingMax英语口语达人

which means that when you say "I'll", you are expressing your intention to do something.

当你使用 "I'll" 的说法时，你是想表示要做某事。

I will 课堂 - SpeakingMax英语口语达人