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FW: [External] : Re: Lexical vs. dynamic: small examples?
From: |
Drew Adams |
Subject: |
FW: [External] : Re: Lexical vs. dynamic: small examples? |
Date: |
Sun, 15 Aug 2021 15:42:21 +0000 |
[Was bitten by Reply All not including the list again...]
> > "Dynamic scope" is a misnomer, BTW; it means only that - no
> > particular scope and dynamic extent [...] `let' provides
> > a lexical binding - the scope ends where the `let'
> > ends, lexically.
>
> But with `let' doesn't the scope end where the let ends even
> for dynamic binding?
No. Dynamic bindings have indefinite scope - that is,
no particular scope.
The binding has dynamic _extent_ - it lasts _as long as_
(time) the code in the `let' body is executing (which
can include nonlocal exits by that code (or code called
by that code) - e.g. `throw').
For such a variable the `let' does not define a scope;
it only determines which code realizes the binding's
duration.
Scope and extent (duration for referencing) are two
different things.
See the CLTL chapter I pointed to.
> If it isn't only about let, what is it about more?
`let' is not the only construct that can define a
scope. For example, a function definition (a `defun'
or a lambda) defines the scope of its formal
parameters - they're lexically scoped.
Again, I recommend that CLTL chapter. It's short, and
it explains things well, including with examples.
<<attachment: winmail.dat>>
- Re: [External] : Re: Lexical vs. dynamic: small examples?, (continued)
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/25
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Stefan Monnier, 2021/08/25
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/25
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/27
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/27
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/15
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Stefan Monnier, 2021/08/15
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/15
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Stefan Monnier, 2021/08/15
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/15
- FW: [External] : Re: Lexical vs. dynamic: small examples?,
Drew Adams <=