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Finite groups of order not divisible by 4 are solvable #2496

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merged 1 commit into from
May 29, 2018

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This is a simple extension of the odd order theorem. See comment
inside the patch.

@fingolfin fingolfin added kind: enhancement Label for issues suggesting enhancements; and for pull requests implementing enhancements topic: library labels May 28, 2018
lib/grp.gi Outdated
## index 2, hence |N| = m.
##
## By the odd order theorem, N is solvable, and so is G. Thus the order of
## any non-solvable finite group is a multiple of 4.
InstallImmediateMethod( IsSolvableGroup, IsGroup and HasSize, 10,
function( G )
G:= Size( G );
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I appreciate that this is not code added in the patch, but personally I really don't like
this reuse of G. Adding a new local variable would add one line of source and 8 bytes of stack frame.

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Agreed.

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and done

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codecov bot commented May 28, 2018

Codecov Report

Merging #2496 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2496      +/-   ##
==========================================
+ Coverage   74.27%   74.27%   +<.01%     
==========================================
  Files         484      484              
  Lines      245343   245343              
==========================================
+ Hits       182217   182218       +1     
+ Misses      63126    63125       -1
Impacted Files Coverage Δ
lib/grp.gi 85.56% <100%> (-0.38%) ⬇️
src/iostream.c 62.64% <0%> (-1.14%) ⬇️
lib/pcgsspec.gi 80.27% <0%> (-0.6%) ⬇️
lib/grplatt.gi 61.66% <0%> (-0.44%) ⬇️
lib/morpheus.gi 82.75% <0%> (-0.12%) ⬇️
lib/grpfp.gi 64.97% <0%> (-0.1%) ⬇️
lib/autsr.gi 31.52% <0%> (ø) ⬆️
src/objset.c 84.82% <0%> (+0.22%) ⬆️
lib/csetgrp.gi 59.31% <0%> (+0.37%) ⬆️
... and 2 more

This is a simple extension of the odd order theorem. See comment
inside the patch.
@fingolfin fingolfin merged commit 1f1186a into gap-system:master May 29, 2018
@fingolfin fingolfin deleted the mh/twice-odd-is-solvable branch May 29, 2018 09:25
@fingolfin fingolfin added the release notes: added PRs introducing changes that have since been mentioned in the release notes label Jul 31, 2018
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