Re: Real-life examples of lexical binding in Emacs Lisp

[Pascal J. Bourguignon]

Robert Thorpe <rt@robertthorpeconsulting.com> writes:

> Emanuel Berg <embe8573@student.uu.se> writes:
>> I take it "lexical" refers to you can make it out by
>> looking at the code.
>
> Yes.
>
>> "Dynamic" refers to it depends on the code and the
>> program state in execution.
>
> Yes.
>
>> I agree those terms are confusing. To me, it sounds
>> like they refer to call-by-value vs.
>> call-by-reference, which isn't so.
>>
>> I'd call it "normal scope" vs.
>> "stacked scope", perhaps.
>
> Both cases are usually implemented using stacks.  Thinking about this
> helps understanding.
>
> In the lexical scope case we can think of one huge stack.  Each entry in
> the stack can contain many elements.  When execution enters a "let" form
> a new entry is created on the stack and the variables declared there are
> stored in that entry.  They "shadow" other variables with the same name
> - they take precedence over them.  When execution exits the let form
> that stack entry is deleted.  This is usually how lexical scope is
> implement too.

However, contrarily to dynamic binding, lexical binding requires the use
of the heap to implement non-delimited closures.

This is why it was less obvious.

-- 
__Pascal Bourguignon__                 http://www.informatimago.com/
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