Re: [Scheme-reports] Draft 3 Comments: Chapter 6

[Alex Shinn <alexshinn@x>]

On Thu, Aug 4, 2011 at 12:46 PM, John Cowan <cowan@x> wrote:
> Alex Shinn scripsit:
>
>>   The initial (or "top level") Scheme environment is empty, and
>>   bindings must be introduced with import.
>>
>> which could indeed be worded better - the implication of the
>> second clause is that `import' is provided.  The initial
>> environment is indeed empty of everything other than `import'.
>
> However, the "initial environment" is *not* the environment in effect
> when the REPL starts up.  That includes at least the base and optionally
> whatever the implementation wishes to provide.
>
> In fact, I do not know what "initial environment" means at all.

It's the environment programs start with.

The result is that any program can be cut&paste into
an interactive REPL and still work, and any interactive
session can be saved and used as a program, so long
as it's prefixed with (import (scheme base)).

It would be cleaner to make the initial REPL env
empty as well (and cleaner still to make importing
out-of-band as in Scheme48), but this contradicts
every existing REPL and would be confusing for
students.

-- 
Alex

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