Re: fn:slice()

I'm currently reading Clean Code[1] from Robert Martin. He says that a 
function should never has more than 3 parameters, and that we should 
make a lot of efforts to avoid functions with more than two parameters. 
Ok, examples in this book are in Java, an OO language, and not a 
functional language, but, in my opinion, as a teacher and a user, I'd 
prefer 3 simple functions with a name that clearly identify what the 
function do, than a function that can make a lot of different things.

Having read this thread over two days let me with a strange fealing : 
I'm not sure I totaly understand what's the goal of this slice function ...

 > We should also be able to write a brief description of the clas in 
about 25 words, without using the words "if", "and", "or", or "but".[2]

I'm not sure we'll be able to give a brief description in 25 words of 
such a swiss-army-knife function.

[1] Clean Code - Robert C. Martin - Pearson Addison-Wesley ISBN-13: 
978-0-13-235088-4
[2] See [1] Chapter 10

Christophe

Le 04/12/2020 à 11:15, Michael Kay a écrit :
> Which do you prefer?
>
> Option A
>
> A single (swiss-army-knife) slice() function as proposed yesterday
>
> Option B
>
> Three functions:
>
> * fn:items-at($seq, xs:integer+) returning the items at the given 
> positions
>
> * fn:slice($seq, start?, step?,  (end | length)? ) accepting some 
> combination of start, end, length, and step, each supplied as an integer
>
> * fn:range($seq, (before | until)? (after | from)?) accepting 
> predicates for the start and/or end of the selected range
>
> This retains most of the useful combinations, but each of the 
> functions is much simpler. (I've used an informal notation to indicate 
> which combinations of parameters are allowed). Negative positions 
> allowed for items-at, start, and end.
>
> Option C
>
> Two functions:
>
> fn:slice($seq, $positions as integer+)
>
> where $positions might be (3), (-1), (1 to 5) or ( 1 to 5 by 2).
>
> fn:range($seq, (before | until)? (after | from)?) accepting predicates 
> for the start and/or end of the selected range
>
>
> Michael Kay
> Saxonica
>
>> On 4 Dec 2020, at 03:52, Mukul Gandhi <gandhi.mukul@gmail.com 
>> <mailto:gandhi.mukul@gmail.com>> wrote:
>>
>> On Fri, Dec 4, 2020 at 8:04 AM Dimitre Novatchev 
>> <dnovatchev@gmail.com <mailto:dnovatchev@gmail.com>> wrote:
>>
>>     While this function is obviously very powerful, its complexity
>>     affects the learning and confidence of use.
>>
>>     This leads to not-confident / hesitant / unhappy developers.
>>
>>
>> I agree to above mentioned concerns.
>>
>> But +1 to introduction of fn:slice() function to XPath/XSLT.
>>
>>
>> -- 
>> Regards,
>> Mukul Gandhi
>