OpenEuphoria

RE: Eu 2.5: new sequence functions

• Posted by Tommy Carlier <tommy.carlier at pandora.be> Jan 13, 2004
• 398 views

Andy Serpa wrote:
> Tommy Carlier wrote:
>> Wouldn't we all like some new (fast as hell) sequence functions?
>> 
>> (length)
>> (append)
>> (prepend)
>> 
>> s = insert(s, i, o) -- insert object o in sequence s at position i
>> s = remove(s, i) -- remove element at position i from sequence s
>> s = replace(s, i, o) -- replace element at position i in sequence s with 
>> 
>> 
>> object o
>> 
>> Wouldn't these 3 little (not so complex) functions add a lot of power to 
>> 
>> 
>> Euphoria and its sequence system? Sure, you can already do them right 
>> now like this:
>> 
>> insert(s, i, o) = s[1..i-1] & o & s[i..length(s)]
>> remove(s, i) = s[1..i-1] & s[i+1..length(s)]
>> replace(s, i, o) = s[1..i-1] & o & s[i+1..length(s)]
>> 
>> But it might be too slow for applications that need pure power. And the 
>> above only works if 1 < i < length(s), so you'd have to check for 
>> boundaries.
>> 
> 
> Actually, they work in all cases.  If the second index of a slice in 
> exactly 1 less than the first, you get the empty sequence.  Perfectly 
> legal (and documented) Euphoria.
> 
> See, you aren't really indexing the elements, but the spaces between 
> them.  The first index refers to the SPACE BEFORE that element, and the 
> second index refers to the SPACE AFTER that element.
> 
> So, in s[1..0], both indexes are actually referencing the same spot, so 
> you get the empty sequence.
> 

Thanks for telling me, I didn't know. But still, these functions are 
very common, don't you think?

And readability of code is very important: I think that 's = replace(s, 
i, o)' is more readable than 's = s[1..i-1] & o & s[i+1..length(s)]'.

And even without the boundary check: these functions as builtin 
system-functions would be a lot faster than the Euphoria-equivalent. And 
more optimizations could be done: I think I read that A=append(A,B) is 
optimized to be faster than A=append(B,C), so A=insert(A,I,O) could also 
be optimized to be faster than A=insert(B,I,O).

And I don't think that they are very complex to implement as builtin 
functions, right Robert? ;-D
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tommy online: http://users.pandora.be/tommycarlier