Re: [Scheme-reports] Write procedure is not backwards compatible

[John Cowan <cowan@x>]

Jonathan Rees scripsit:

> May I suggest splitting "Language changes since R5RS" into two parts:
> 1. What someone needs to know when porting from R5RS to R7RS
> (i.e. incompatible changes)
> 2. What someone who knows R5RS would need to learn when reading R7RS
> programs (mostly compatible extensions I hope)
> Looks like #1 will be quite short, but the relevant items are currently
> spread around.

Editorial ticket #446 filed.

> Similarly, R6RS-main incompatibilities may fall into classes,
> although it looks like most of the ones listed are either retractions,
> limitations, or "R7RS doesn't have x but it has y instead". Maybe
> there are extensions that aren't listed here because they're in the
> R5RS-diff section?

This list is meant to be incompatibilities only, not compatible
extensions.

> A bit more detail on the bullet "Case insensitivity is now the default"
> would be helpful, since it's hard to tell from reading R5RS what its
> position is on the subject.

Section 2 of R5RS says "Upper and lower case forms of a letter are
never distinguished except within character and string constants. For
example, Foo is the same identifier as FOO, and #x1AB is the same number
as #X1ab."  I don't see any way to misinterpret that.

> If there are putatively conformant case-sensitive R5RS implementations

There are a bunch of implementations which are R5RS-conformant except for
case sensitivity, which I think is why case sensitivity became part of
both R6RS and R7RS.  See http://trac.sacrideo.us/wg/wiki/CaseInsensitivity
for details.

> then this is an incompatible change and you should say so.

It is indeed an incompatible change.

-- 
I Hope, Sir, that we are not                    John Cowan
mutually Un-friended by this                    cowan@x
Difference which hath happened                  http://www.ccil.org/~cowan
betwixt us.     --Thomas Fuller, Appeal to Injured Innocence (1659)

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