Roger, To explain f would you call } item amend rather than amend ?
]a=: 100 (2 4 5}) a=:i.10
0 1 100 3 100 100 6 7 8 9
f=: 13 :'x (2 4 5}) y'
100 f i.10
0 1 100 3 100 100 6 7 8 9
Here's the example that is puzzling me.
*i.5
0 1 1 1 1
*/"0 i.5
0 1 2 3 4
Linda
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Henry Rich
Sent: Tuesday, September 09, 2014 4:54 PM
To: [email protected]
Subject: Re: [Jprogramming] Replace one item of a list
I don't think Ian meant, or said, that amend-in-place violates any
rules. He said
[J] actually does in-place updating (even though, at face value,
J syntax does not permit such a thing).
The key words are "at face value". I take that to mean that a
beginner-to-advanced user, looking at the description of m}, would think
that it always produces a complete new array.
Ian's post makes it clear that he considering the inexpert J
programmer's view of J.
Henry Rich
On 9/9/2014 12:35 PM, Roger Hui wrote:
> I don't believe the messages you cited explained it. J syntax consists of
> word formation as defined by ;: and parsing rules as defined by Section
IIE
> of the dictionary. How is amend-in-place not permitted by either part?
>
>
>
> On Tue, Sep 9, 2014 at 8:56 AM, Dan Bron <[email protected]> wrote:
>
>> Ian wrote:
>>> Then it actually does in-place updating (even though,
>>> at face value, J syntax does not permit such a thing).
>>
>> Roger responded:
>>> Please explain why this is not permitted by J syntax.
>>
>> I believe Ian is expressing a thought recently raised by Erling Hellenas
in
>> [1], which I responded to here:
>>
>> http://www.jsoftware.com/pipermail/programming/2014-July/038030.html
>>
>> -Dan
>>
>> [1] "J and indexed replacement":
>>
http://www.jsoftware.com/pipermail/programming/2014-July/038068.html
>>
>> "In most languages indexed replacement is indexed replacement? In J
>> and
>> in most functional languages it is not? You get a brand new
variable?
>> So, why give the user the flawed impression he can still do
indexed
>> replacement and do amendments to variables/nouns? And at the same
>> time
>> in tacit code we pretend to only have functions? No
variables/nouns
>> to
>> be amended? Just functional transformations?"
>>
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