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Re: [PATCH] Bring `bitwise-copy-bit' behavior back in line with R6RS.

From: Mark H Weaver
Subject: Re: [PATCH] Bring `bitwise-copy-bit' behavior back in line with R6RS.
Date: Mon, 18 Sep 2017 01:50:24 -0400
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux)

Julian Graham <address@hidden> writes:

> It looks like there was a subtle but significant regression introduced
> to the behavior of `bitwise-copy-bit' in `(rnrs arithmetic bitwise)'
> back in 93da406f33.
> R6RS says [0] that function (with arguments EI1, EI2, EI3) should
> transfer the EI2th bit from EI3 to EI1, but Guile's implementation was
> always reading the 0th bit from EI3.

I was puzzled by this, because the same specification also states that
"ei3 must be either 0 or 1", which clearly contradicts the part that you
quoted, so I checked the R6RS errata.  Here's what it says:


    In the specification of bitwise-copy-bit,
    "[...] by the ei2 bit of ei3"
    should be replaced by
    "[...] by ei3"

So, I don't think there's a problem here.  Please let me know if there's
something I've missed.


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