Il giorno 18/mag/2015, alle ore 21.34, Jens Axel Søgaard ha scritto:
2015-05-18 21:25 GMT+02:00 Michael Tiedtke michael.tied...@o2online.de:
Il giorno 18/mag/2015, alle ore 20.50, Jos Koot ha scritto:
I think Rackets's reference and guide are *very clear* about eq?, eqv? and
equal?.
Structure and Interpretation of Computer Programs (sicp2) about sameness:
https://mitpress.mit.edu/sicp/full-text/book/book-Z-H-16.html#footnote_Temp_230
We can consider two symbols to be ``the same'' if they consist of the same
characters in the same order. Such a definition skirts a deep
SICP isn' the bible, especially not on programming language knowledge. I'd
recommend checking out relevant literature instead.
On May 18, 2015, at 8:24 AM, Michael Tiedtke michael.tied...@o2online.de
wrote:
Structure and Interpretation of Computer Programs (sicp2) about sameness:
George Neuner gneun...@comcast.net writes:
Hi,
On 5/17/2015 5:32 PM, Atticus wrote:
---
$ racket
Welcome to Racket v6.1.1.
(eq? 'l 'l)
#f
(eq? 'l 'l)
#t
$ racket --no-jit
Welcome to Racket v6.1.1.
(eq? 'l 'l)
#f
(eq? 'l 'l)
#t
(eq? 'l 'l)
#f
Il giorno 18/mag/2015, alle ore 18.06, Atticus ha scritto:
I guess it's a matter of definition. I must admit that i didn't reflect
on equality that much.
My (very limited) knowledge about that stuff comes mostly from the The
Little Schemer which imho explains it really well with the 'eqan?'
I guess it's a matter of definition. I must admit that i didn't reflect
on equality that much.
My (very limited) knowledge about that stuff comes mostly from the The
Little Schemer which imho explains it really well with the 'eqan?' and
'eqlist?' procedure.
The reason why i checked (eq? 'symbol1
even an
unsolvable thing.
Jos
-Original Message-
From: racket-users@googlegroups.com [mailto:racket-users@googlegroups.com]
On Behalf Of Michael Tiedtke
Sent: lunes, 18 de mayo de 2015 19:00
To: racket-users@googlegroups.com
Subject: Re: [racket-users] Strange behaviour of the eq
In my early time learning Racket, I wish someone had given me the
following advice:
For now? Just use `equal?`.
`equal?` will usually do the right thing, including for numbers,
strings, symbols, immutable lists, and so on. A type-specific function
like `=` or `string-=?` might be a bit faster.
Il giorno 18/mag/2015, alle ore 20.50, Jos Koot ha scritto:
I think Rackets's reference and guide are *very clear* about eq?, eqv? and
equal?.
Yes, right. It was the Racket Reference to tell me exactly that eqv? is an eq?
that
works for numbers and characters, too. I really had to look this
2015-05-18 21:25 GMT+02:00 Michael Tiedtke michael.tied...@o2online.de:
Il giorno 18/mag/2015, alle ore 20.50, Jos Koot ha scritto:
I think Rackets's reference and guide are *very clear* about eq?, eqv?
and
equal?.
Yes, right. It was the Racket Reference to tell me exactly that eqv? is
of
equality.
Jos
-Original Message-
From: racket-users@googlegroups.com [mailto:racket-users@googlegroups.com]
On Behalf Of Greg Hendershott
Sent: lunes, 18 de mayo de 2015 20:56
To: racket-users@googlegroups.com
Subject: Re: [racket-users] Strange behaviour of the eq? operator in racket
repl
In my
On May 18, 2015, at 1:19 AM, Michael Tiedtke michael.tied...@o2online.de
wrote:
I'm new to Racket but even R5RS is rather clear about this issue:
(citation from doc/r5rs/r5rs-std/r5rs-Z-H-9.html)
(eq? 2 2) === unspecified
In Racket, (eq? 2 2) is specified as true.
It says here:
[mailto:michael.tied...@o2online.de]
Sent: lunes, 18 de mayo de 2015 21:26
To: Jos Koot; racket-users@googlegroups.com
Subject: Re: [racket-users] Strange behaviour of the eq? operator in racket
repl
snip
Maybe, I never thought about that in mathematical terms if not with the
concept
of identity. How could
On Mon, May 18, 2015 at 08:50:50PM +0200, Jos Koot wrote:
At the mathematical level equality is a difficult and in many cases even an
unsolvable thing.
Indeed. It is suspected by some that difficulties with equality lie at
the root of problems with set theory.
There are two concepts of
Yes, Scheme (and therefore Racket) has eq?, eqv?, and equal?. I understand the
desire for eq? and equal?, but I’ve always been skeptical of the necessity of
eqv?. Either way, Scheme left this behavior unspecified, but I believe Racket
specifies it (though I could be wrong).
Racket has two
I'm new to Racket but even R5RS is rather clear about this issue:
(citation from doc/r5rs/r5rs-std/r5rs-Z-H-9.html)
(eq? 2 2) === unspecified
Rationale: It will usually be possible to implement eq? much more
efficiently than eqv?, for example, as a simple pointer comparison instead of
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