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Feature #966

New function or explain: first and last for a vector?

Added by Anna Maria Bigatti over 7 years ago. Updated about 4 years ago.

Status:
Closed
Priority:
Normal
Assignee:
Anna Maria Bigatti
Category:
Documentation
Target version:
CoCoALib-0.99700
Start date:
10 Nov 2016
Due date:
% Done:

100%

Estimated time:
2.22 h
Spent time:
2.15 h

Description

In CoCoA-5 we often first and last for making sub-lists.
This is tedious to translate into C++.
Make good C++ documentation, or write a trivial/inefficient function for handy-handling of short lists.

Related issues

Related to CoCoALib - Feature #357: Constructor for vectors? CoCoAVectorRejected2013-05-24

History

#1 Updated by Anna Maria Bigatti over 7 years ago

  • Related to Feature #357: Constructor for vectors? CoCoAVector added

#2 Updated by Anna Maria Bigatti over 7 years ago

  • Assignee set to Anna Maria Bigatti

Equivalent to first,last:

vector<RingElem>(x.begin(), x.end()-1))
vector<RingElem>(x.begin()+2, x.end()))

#3 Updated by John Abbott over 7 years ago

I am not yet convinced that first and last are good ideas for C++.

What exactly are the hoped-for semantics? Maybe last can be implemented relatively efficiently, but I have doubts about first.
I am concerned that they may make wasteful copies of the elements of the list/vector.

#4 Updated by Anna Maria Bigatti over 7 years ago

John Abbott wrote:

I am concerned that they may make wasteful copies of the elements of the list/vector.

Surely they do make wasteful copies. That's why I wrote "short lists" ;-)
Anyway, I'm adding some examples in ex-c++.

#5 Updated by Anna Maria Bigatti over 5 years ago

  • Category changed from New Function to Documentation
  • Status changed from New to In Progress
  • Target version changed from CoCoALib-1.0 to CoCoALib-0.99650 November 2019
  • % Done changed from 0 to 20

#6 Updated by Anna Maria Bigatti over 5 years ago

  • Subject changed from New function: first and last for a vector? to New function or explain: first and last for a vector?

#7 Updated by John Abbott over 4 years ago

  • Target version changed from CoCoALib-0.99650 November 2019 to CoCoALib-0.99700

#8 Updated by Anna Maria Bigatti over 4 years ago

  • Status changed from In Progress to Resolved
  • % Done changed from 20 to 70

OK, I think we should not make a function in lib.
I added an example in ex-c++.C.

Now I realized that there is a ex-c++-vector.C, so I think my original example should be split into the specific example files.

... not today.
In time for next release? not sure.

#9 Updated by John Abbott about 4 years ago

  • Status changed from Resolved to Closed
  • % Done changed from 70 to 100
  • Estimated time changed from 3.00 h to 2.22 h

I have moved the example into a new file ex-c++-vector2.C which illustrates how to "translate" the CoCoA-5 functions append, first and last into C++.

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