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Re: [Bug-apl] Identify function


From: David Lamkins
Subject: Re: [Bug-apl] Identify function
Date: Tue, 1 Jul 2014 10:02:18 -0700

Further insights here:

http://aplwiki.com/Left,%20Right,%20or%20the%20Same%3F


BTW, note that ISO APL conjugate returns DOMAIN ERROR for a non-numeric argument. When Dyalog introduced the identity function, they deprecated use of + as identity; perhaps they're attempting to move closer to standards conformance in this case.



On Tue, Jul 1, 2014 at 9:56 AM, Elias Mårtenson <address@hidden> wrote:
Exactly, and since an identity function is useful it makes sense to map it to the same symbol as Dyalog.

Regards,
Elias


On 2 July 2014 00:55, David Lamkins <address@hidden> wrote:
Digging further, it's interesting to note that ISO APL defines + as conjugate, but does not have a binding for the identity function.


On Tue, Jul 1, 2014 at 9:42 AM, David Lamkins <address@hidden> wrote:
I looked this up yesterday. Dialog version 13 introduced the use of the tack as identity and repurposed + as conjugate. (Actually, they bound both left and right tacks identically, even though they call left tack "same" and right tack "identity".) If the argument of conjugate is imaginary, conjugate returns the number with the imaginary part negated. If the argument of conjugate is real or non-numeric, conjugate returns the argument unchanged.




From: Juergen Sauermann <address@hidden>
To: "Elias Mårtenson" <address@hidden>
Cc: "address@hidden" <address@hidden>
Date: Tue, 01 Jul 2014 17:04:24 +0200
Subject: Re: [Bug-apl] Identify function
Hi Elias,

I looked in "Mastering APL" from Dyalog and could not find it.
They call + the identity function.

And what would be the use of it?

/// Jürgen


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