ChainComplexes: Add map/object_range/extract; fix start and show

[AlexD97]

[codecov[bot]]

Codecov Report

Merging #774 (9c3bd3b) into master (c9a106b) will increase coverage by 0.03%. The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #774      +/-   ##
==========================================
+ Coverage   72.30%   72.33%   +0.03%     
==========================================
  Files         342      342              
  Lines       97904    97947      +43     
==========================================
+ Hits        70789    70851      +62     
+ Misses      27115    27096      -19     

Impacted Files	Coverage Δ
src/GrpAb/ChainComplex.jl	0.00% <0.00%> (ø)
src/NumFieldOrd/NfOrd/Clgp.jl	79.37% <0.00%> (-1.80%)	:arrow_down:
src/NumField/NfRel/NfRelNSMor.jl	78.57% <0.00%> (-1.54%)	:arrow_down:
src/NumFieldOrd/NfOrd/Ideal/TwoElement.jl	57.03% <0.00%> (-1.45%)	:arrow_down:
src/LocalField/neq.jl	76.76% <0.00%> (-1.02%)	:arrow_down:
src/NumFieldOrd/NfOrd/LinearAlgebra.jl	54.25% <0.00%> (-0.48%)	:arrow_down:
src/Misc/RatRecon.jl	18.91% <0.00%> (-0.39%)	:arrow_down:
src/QuadForm/Herm/Lattices.jl	95.71% <0.00%> (-0.24%)	:arrow_down:
src/GrpAb/GrpAbFinGen.jl	73.18% <0.00%> (-0.22%)	:arrow_down:
src/AlgAssRelOrd/Order.jl	62.93% <0.00%> (-0.22%)	:arrow_down:
... and 21 more

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[thofma]

Is it expected that the Oscar tests will fail with this? Just asking so we know how to proceed.

[jankoboehm]

It fixes the print function for complexes (so printout will change), introduces functions for map and object range, and to extract parts of the complex using map and object range, also a shift operation for the degree. These functions are not used yet in OSCAR, but will be used in a PR to come. ChainComplex is exported to help to improve the docu in Oscar avoiding to write Hecke.

[thofma]

This PR here makes the OSCAR tests fail: https://github.com/thofma/Hecke.jl/runs/7788161199?check_suite_focus=true#step:7:799

Is this intentional?

[jankoboehm]

No it should not. We have to check, it can be that we have to do an update on the OSCAR side.

[AlexD97]

Yes, it should break the tests in UngradedModules.jl. They will then be fixed with another PR.

[jankoboehm]

We will make the PR for OSCAR. Once everyhting is right there this one can be merged. Then the one in Oscar.

[AlexD97]

https://github.com/oscar-system/Oscar.jl/pull/1508 should fix the failing tests.