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Fixed typos and function name that were admonished.
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hulpke committed Apr 17, 2018
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2 changes: 1 addition & 1 deletion doc/ref/algfld.xml
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Expand Up @@ -102,7 +102,7 @@ gap> m^2;
<Section Label="Finding Subfields">
<Heading>Finding Subfields</Heading>

<#Include Label="DecomPoly">
<#Include Label="IdealDecompositionsOfPolynomial">

</Section>
</Chapter>
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18 changes: 9 additions & 9 deletions lib/algfld.gd
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Expand Up @@ -190,19 +190,19 @@ DeclareGlobalFunction("AlgExtSquareHensel");

#############################################################################
##
#F DecomPoly( <f> [:"onlyone"] ) finds ideal decompositions of rational f
#F IdealDecompositionsOfPolynomial( <f> [:"onlyone"] ) finds ideal decompositions of rational f
##
## <#GAPDoc Label="DecomPoly">
## <#GAPDoc Label="IdealDecompositionsOfPolynomial">
## <ManSection>
## <Func Name="DecomPoly" Arg='pol'/>
## <Func Name="IdealDecompositionsOfPolynomial" Arg='pol'/>
##
## <Description>
## Let <M>f</M> be a univariate, rational, irreducible, polynomial. A
## pair <M>g</M>,<M>h</M> of polynomials of degree strictly
## smaller than that of <M>f</M>, such that <M>f(x)|g(h(x))</M> is
## called an ideal decomposition. In the context of field
## extensions, if <M>\alpha</M> is a root of <M>f</M> in a suitable extension
## and <M>Q</M> the field of rational numbers, such a decomposition corresponds
## and <M>Q</M> the field of rational numbers. Such decompositions correspond
## to (proper) subfields <M>Q\lt Q(\beta)\lt Q(\alpha)</M>, where <M>g</M> is the
## minimal polynomial of <M>\beta</M>.
## This function determines such decompositions up to equality of the subfields
Expand All @@ -212,21 +212,21 @@ DeclareGlobalFunction("AlgExtSquareHensel");
## most one such decomposition (and performs faster).
## <Example><![CDATA[
## gap> x:=X(Rationals,"x");;pol:=x^8-24*x^6+144*x^4-288*x^2+144;;
## gap> l:=DecomPoly(pol);
## gap> l:=IdealDecompositionsOfPolynomial(pol);
## [ [ x^2+72*x+144, x^6-20*x^4+60*x^2-36 ],
## [ x^2-48*x+144, x^6-21*x^4+84*x^2-48 ],
## [ x^2+288*x+17280, x^6-24*x^4+132*x^2-288 ],
## [ x^4-24*x^3+144*x^2-288*x+144, x^2 ] ]
## gap> List(l,x->Value(x[1],x[2])/pol);
## [ x^4-16*x^2-8, x^4-18*x^2+33, x^4-24*x^2+120, 1 ]
## gap> DecomPoly(pol:onlyone);
## gap> IdealDecompositionsOfPolynomial(pol:onlyone);
## [ [ x^2+72*x+144, x^6-20*x^4+60*x^2-36 ] ]
## ]]></Example>
## In this example the given polynomial is regular with Galois group
## <M>Q_8</M>, thus exposing the four proper subfields.
## <M>Q_8</M>, as expected we get four proper subfields.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareGlobalFunction("DecomPoly");

DeclareGlobalFunction("IdealDecompositionsOfPolynomial");
DeclareSynonym("DecomPoly",IdealDecompositionsOfPolynomial);
4 changes: 2 additions & 2 deletions lib/algfld.gi
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Expand Up @@ -2194,10 +2194,10 @@ end);

#############################################################################
##
#F DecomPoly( <f> [,"onlyone"] ) finds ideal decompositions of rational f
#F IdealDecompositionsOfPolynomial( <f> [,"onlyone"] ) finds ideal decompositions of rational f
## This is equivalent to finding subfields of K(alpha).
##
InstallGlobalFunction(DecomPoly,function(f)
InstallGlobalFunction(IdealDecompositionsOfPolynomial,function(f)
local n,e,ff,p,ffp,ffd,roots,allroots,nowroots,fm,fft,comb,combi,k,h,i,j,
gut,avoid,blocks,g,m,decom,z,R,scale,allowed,hp,hpc,a,kfam,only;

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5 changes: 4 additions & 1 deletion lib/grp.gd
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Expand Up @@ -4543,14 +4543,17 @@ DeclareOperation( "LowIndexSubgroups",
## provided only as a separate function, and not as method for the operation
## <C>Normalizer</C>, as it can often be slower than other built-in routines.
## In certain hard cases (non-solvable groups with nontrivial radical), however
## its performance is substantially superior. The function thus provided as a
## its performance is substantially superior.
## The function thus is provided as a
## non-automated tool for advanced users.
## <Example><![CDATA[
## gap> g:=TransitiveGroup(30,2030);;
## gap> s:=SylowSubgroup(g,5);;
## gap> Size(NormalizerViaRadical(g,s));
## 28800
## ]]></Example>
## Note that this example only demonstartes usage, but that in this case
## in fact the ordinary <C>Normalizer</C> routine performs faster.
## </Description>
## </ManSection>
## <#/GAPDoc>
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