x It says, take the name x and create a binding for that name to the value of the sub-expression and in fact to do this, to stress a point, let's do that.

它的意思是，创建了一个名字,然后创建了对于这个名字,和子表达式的值的绑定,实际上这么做，我们是为了，要强调一个点，让我们来说说这个点。

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which I just did there, -mystring in fact, let me type it in-- mystring, with an equal sign, which is saying, assign or bind to that name the value of the following expression.

也就是这里我做的，实际上，让我输入，然后是个蹬好，意思就是说，把这个名字绑定到,后面表达式的值上去。

麻省理工公开课 - 计算机科学及编程导论课程节选