extension of vecextract()

[Igor Schein <igor@txc.com>]

Hi,

let's say I have a vector and I wanna insert an element into it:

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? v=["a","b","c","d"];

\\ inserting an element at 3rd position:

? concat([vecextract(v,3),[1],vecextract(v,12)])
["a", "b", 1, "c", "d"]
\\ or
? w=[1,2];concat([vecextract(v,w),[1],vecextract(v,eval(setminus(Set(vector(4,k,k)),Set(w))))])
["a", "b", 1, "c", "d"]
\\ or
? concat([vecextract(v,"1..2"),[1],vecextract(v,"3..4")])
["a", "b", 1, "c", "d"]

\\ however, if I wanna insert it in the beginning or in the end:

? concat([vecextract(v,15),[1],vecextract(v,0)])
["a", "b", "c", "d", 1]
\\ or
? w=[1,2,3,4];concat([vecextract(v,w),[1],vecextract(v,eval(setminus(Set(vector(4,k,k)),w)))])
["a", "b", "c", "d", 1]
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There's no way to do it with ".." mechanism

So maybe it's a good idea to extend ".." mechanism to be consistent
with the other two? 

Thanks

Igor