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#############################################################################
##
## This file is part of GAP, a system for computational discrete algebra.
## This file's authors include Frank Celler.
##
## Copyright of GAP belongs to its developers, whose names are too numerous
## to list here. Please refer to the COPYRIGHT file for details.
##
## SPDX-License-Identifier: GPL-2.0-or-later
##
## This file contains the basic operations for creating and doing arithmetic
## with vectors.
##

#############################################################################
##
#v GF2One . . . . . . . . . . . . . . . . . . . . . . . . . . one of GF(2)
##
BIND_GLOBAL( "GF2One", Z(2) );

#############################################################################
##
#v GF2Zero . . . . . . . . . . . . . . . . . . . . . . . . . . zero of GF(2)
##
BIND_GLOBAL( "GF2Zero", 0*Z(2) );

#############################################################################
##
#R IsGF2VectorRep( <obj> ) . . . . . . . . . . . . . . . . . vector over GF2
##
## <#GAPDoc Label="IsGF2VectorRep">
## <ManSection>
## <Filt Name="IsGF2VectorRep" Arg='obj' Type='Representation'/>
##
## <Description>
## An object <A>obj</A> in <Ref Filt="IsGF2VectorRep"/> describes
## a vector object (see <Ref Filt="IsVectorObj"/>) with entries in the
## finite field with <M>2</M> elements.
## 
## <Ref Filt="IsGF2VectorRep"/> implies <Ref Filt="IsCopyable"/>,
## thus vector objects in this representation can be mutable.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
## <Ref Filt="IsGF2VectorRep"/> is a subrepresentation of
## <Ref Filt="IsDataObjectRep"/>, the entries are packed into bits.
##
DeclareRepresentation( "IsGF2VectorRep",
 IsDataObjectRep and IsVectorObj
 and IsCopyable
 and IsNoImmediateMethodsObject
 and HasBaseDomain and HasOneOfBaseDomain and HasZeroOfBaseDomain);

#############################################################################
##
#F ConvertToGF2VectorRep( <vector> ) . . . . . . . . convert representation
##
## <ManSection>
## <Func Name="ConvertToGF2VectorRep" Arg='vector'/>
##
## <Description>
## </Description>
## </ManSection>
##
DeclareSynonym( "ConvertToGF2VectorRep", CONV_GF2VEC );

#############################################################################
##
#F ConvertToVectorRep( <list>[, <field>] )
#F ConvertToVectorRep( <list>[, <fieldsize>] )
#F ConvertToVectorRepNC( <list>[, <field>] )
#F ConvertToVectorRepNC( <list>[, <fieldsize>] )
##
## <#GAPDoc Label="ConvertToVectorRep">
## <ManSection>
## <Heading>ConvertToVectorRep</Heading>
## <Func Name="ConvertToVectorRep" Arg='list[, field]'
## Label="for a list (and a field)"/>
## <Func Name="ConvertToVectorRep" Arg='list[, fieldsize]'
## Label="for a list (and a prime power)"/>
## <Func Name="ConvertToVectorRepNC" Arg='list[, field]'
## Label="for a list (and a field)"/>
## <Func Name="ConvertToVectorRepNC" Arg='list[, fieldsize]'
## Label="for a list (and a prime power)"/>
##
## <Description>
## Called with one argument <A>list</A>,
## <Ref Func="ConvertToVectorRep" Label="for a list (and a field)"/>
## converts <A>list</A> to an internal row vector representation
## if possible.
## 
## Called with a list <A>list</A> and a finite field <A>field</A>,
## <Ref Func="ConvertToVectorRep" Label="for a list (and a field)"/>
## converts <A>list</A> to an internal row vector representation appropriate
## for a row vector over <A>field</A>.
## 
## Instead of a <A>field</A> also its size <A>fieldsize</A> may be given.
## 
## It is forbidden to call this function unless <A>list</A> is a plain
## list or a row vector, <A>field</A> is a field, and all elements
## of <A>list</A> lie in <A>field</A>.
## Violation of this condition can lead to unpredictable behaviour or a
## system crash.
## (Setting the assertion level to at least 2 might catch some violations
## before a crash, see <Ref Func="SetAssertionLevel"/>.)
## 
## <A>list</A> may already be a compressed vector. In this case, if no
## <A>field</A> or <A>fieldsize</A> is given, then nothing happens. If one is
## given then the vector is rewritten as a compressed vector over the
## given <A>field</A> unless it has the filter
## <C>IsLockedRepresentationVector</C>, in which case it is not changed.
## 
## The return value is the size of the field over which the vector
## ends up written, if it is written in a compressed representation.
## 
## In this example, we first create a row vector and then ask &GAP; to
## rewrite it, first over <C>GF(2)</C> and then over <C>GF(4)</C>.
## 
## <Example><![CDATA[
## gap> v := [Z(2)^0,Z(2),Z(2),0*Z(2)];
## [ Z(2)^0, Z(2)^0, Z(2)^0, 0*Z(2) ]
## gap> RepresentationsOfObject(v);
## [ "IsPlistRep", "IsInternalRep" ]
## gap> ConvertToVectorRep(v);
## 2
## gap> v;
## <a GF2 vector of length 4>
## gap> ConvertToVectorRep(v,4);
## 4
## gap> v;
## [ Z(2)^0, Z(2)^0, Z(2)^0, 0*Z(2) ]
## gap> RepresentationsOfObject(v);
## [ "IsDataObjectRep", "Is8BitVectorRep" ]
## ]]></Example>
## 
## A vector in the special representation over <C>GF(2)</C> is always viewed
## as <C><a GF2 vector of length ...></C>.
## Over fields of orders 3 to 256, a vector of length 10 or less is viewed
## as the list of its coefficients, but a longer one is abbreviated.
## 
## Arithmetic operations (see <Ref Sect="Arithmetic for Lists"/> and
## the following sections) preserve the compression status of row vectors in
## the sense that if all arguments are compressed row vectors written over
## the same field and the result is a row vector then also the result is a
## compressed row vector written over this field.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareGlobalFunction( "ConvertToVectorRepNC");
DeclareSynonym( "ConvertToVectorRep",ConvertToVectorRepNC);

# TODO: The following two functions only exist in HPC-GAP, but we always
# declare them so that other code can access them conditionally, inside
# an "if IsHPCGAP", without triggering syntax warnings about
# unbound global variables.
DeclareGlobalFunction( "CopyToVectorRep");
DeclareGlobalFunction( "CopyToVectorRepNC");

#############################################################################
##
#F ConvertToMatrixRep( <list>[, <field>] )
#F ConvertToMatrixRep( <list>[, <fieldsize>] )
#F ConvertToMatrixRepNC( <list>[, <field>] )
#F ConvertToMatrixRepNC( <list>[, <fieldsize>] )
##
## <#GAPDoc Label="ConvertToMatrixRep">
## <ManSection>
## <Func Name="ConvertToMatrixRep" Arg='list[, field]'
## Label="for a list (and a field)"/>
## <Func Name="ConvertToMatrixRep" Arg='list[, fieldsize]'
## Label="for a list (and a prime power)"/>
## <Func Name="ConvertToMatrixRepNC" Arg='list[, field]'
## Label="for a list (and a field)"/>
## <Func Name="ConvertToMatrixRepNC" Arg='list[, fieldsize]'
## Label="for a list (and a prime power)"/>
##
## <Description>
##
## This function is more technical version of <Ref Oper="ImmutableMatrix"/>,
## which will never copy a matrix (or any rows of it) but may fail if it
## encounters rows locked in the wrong representation, or various other
## more technical problems. Most users should use <Ref Oper="ImmutableMatrix"/>
## instead. The NC versions of the function do less checking of the
## argument and may cause unpredictable results or crashes if given
## unsuitable arguments.
##
## Called with one argument <A>list</A>,
## <Ref Func="ConvertToMatrixRep" Label="for a list (and a field)"/>
## converts <A>list</A> to an internal matrix representation
## if possible.
## 
## Called with a list <A>list</A> and a finite field <A>field</A>,
## <Ref Func="ConvertToMatrixRep" Label="for a list (and a field)"/>
## converts <A>list</A> to an internal matrix representation appropriate
## for a matrix over <A>field</A>.
## 
## Instead of a <A>field</A> also its size <A>fieldsize</A> may be given.
## 
## It is forbidden to call this function unless all elements of <A>list</A>
## are row vectors with entries in the field <A>field</A>.
## Violation of this condition can lead to unpredictable behaviour or a
## system crash.
## (Setting the assertion level to at least 2 might catch some violations
## before a crash, see <Ref Func="SetAssertionLevel"/>.)
## 
## <A>list</A> may already be a compressed matrix. In this case, if no
## <A>field</A> or <A>fieldsize</A> is given, then nothing happens.
## 
## The return value is the size of the field over which the matrix
## ends up written, if it is written in a compressed representation.
## 
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareGlobalFunction( "ConvertToMatrixRepNC" );
DeclareGlobalFunction( "ConvertToMatrixRep" );

#############################################################################
##
#R IsGF2MatrixRep( <obj> ) . . . . . . . . . . . . . . . . . matrix over GF2
##
## <#GAPDoc Label="IsGF2MatrixRep">
## <ManSection>
## <Filt Name="IsGF2MatrixRep" Arg='obj' Type='Representation'/>
##
## <Description>
## An object <A>obj</A> in <Ref Filt="IsGF2MatrixRep"/> describes
## a matrix object (see <Ref Filt="IsMatrixObj"/>) with entries in the
## finite field with <M>2</M> elements, which behaves like the
## list of its rows (see <Ref Filt="IsRowListMatrix"/>).
## The base domain of <A>obj</A> is the field with <M>2</M> elements.
## 
## <Ref Filt="IsGF2MatrixRep"/> implies <Ref Filt="IsCopyable"/>,
## thus vector objects in this representation can be mutable.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
## <A>obj</A> is internally represented as a positional object
## (see <Ref Filt="IsPositionalObjectRep"/>).
## If the number of rows is <M>n</M> then this object stores <M>n+1</M>
## entries,
## <M>n</M> at position <M>1</M> and the <M>i</M>-th row at position
## <M>i+1</M>.
##
DeclareRepresentation( "IsGF2MatrixRep",
 IsPositionalObjectRep and IsRowListMatrix
 and IsCopyable
 and IsNoImmediateMethodsObject
 and HasNumberRows and HasNumberColumns
 and HasBaseDomain and HasOneOfBaseDomain and HasZeroOfBaseDomain);

#############################################################################
##
#M IsOrdinaryMatrix( <obj> )
#M IsConstantTimeAccessList( <obj> )
#M IsSmallList( <obj> )
##
## Lists in `IsGF2VectorRep' and `IsGF2MatrixRep' are (at least) as good
## as lists in `IsInternalRep' w.r.t.~the above filters.
##
InstallTrueMethod( IsConstantTimeAccessList, IsList and IsGF2VectorRep );
InstallTrueMethod( IsSmallList, IsList and IsGF2VectorRep );

InstallTrueMethod( IsOrdinaryMatrix, IsMatrix and IsGF2MatrixRep );
InstallTrueMethod( IsConstantTimeAccessList, IsList and IsGF2MatrixRep );
InstallTrueMethod( IsSmallList, IsList and IsGF2MatrixRep );

#############################################################################
##
#F ConvertToGF2MatrixRep( <matrix> ) . . . . . . . . convert representation
##
## <ManSection>
## <Func Name="ConvertToGF2MatrixRep" Arg='matrix'/>
##
## <Description>
## </Description>
## </ManSection>
##

DeclareSynonym( "ConvertToGF2MatrixRep", CONV_GF2MAT);

#############################################################################
##
#F ImmutableMatrix( <field>, <matrix>[, <change>] ) . convert into "best" representation
##
## <#GAPDoc Label="ImmutableMatrix">
## <ManSection>
## <Oper Name="ImmutableMatrix" Arg='field, matrix[, change]'/>
##
## <Description>
## Let <A>matrix</A> be an object for which either <Ref Filt="IsMatrix"/> or
## <Ref Filt="IsMatrixObj"/> returns <K>true</K>.
## In the former case, <A>matrix</A> is a list of lists,
## and <Ref Oper="ImmutableMatrix"/> returns an immutable object for which
## <Ref Filt="IsMatrix"/> returns <K>true</K> (in particular again a list of
## lists), which is equal to <A>matrix</A>,
## and which is in the optimal (concerning space and runtime) representation
## for matrices defined over <A>field</A>,
## provided that the entries of <A>matrix</A> lie in <A>field</A>.
## In the latter case, <Ref Oper="ImmutableMatrix"/> returns an immutable
## object that is equal to the result of
## <Ref Oper="ChangedBaseDomain" Label="for a matrix object"/>
## when this is called with <A>matrix</A> and <A>field</A>.
## 
## This means that matrices obtained by several calls of
## <Ref Oper="ImmutableMatrix"/> for the same <A>field</A> are compatible
## for fast arithmetic without need for field conversion.
## 
## If the input matrix <A>matrix</A> is in <Ref Filt="IsMatrix"/>
## then it or its rows might change their representation as a side effect
## of this function.
## However, one cannot rely on this side effect.
## Also, if <A>matrix</A> is already immutable and the result of
## <Ref Oper="ImmutableMatrix"/> has the same internal representation as
## <A>matrix</A>, the result is not necessarily <E>identical</E> to
## <A>matrix</A>.
## 
## If <A>change</A> is <K>true</K>, <A>matrix</A> or its rows (if there are
## subobjects that represent rows) may be changed to become immutable;
## otherwise the rows of <A>matrix</A> are copied first.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareOperation( "ImmutableMatrix",[IsObject,IsMatrix]);

#############################################################################
##
#F ImmutableVector( <field>, <vector>[, <change>] ) . convert into "best" representation
##
## <#GAPDoc Label="ImmutableVector">
## <ManSection>
## <Oper Name="ImmutableVector" Arg='field, vector[, change]'/>
##
## <Description>
## Let <A>vector</A> be an object for which <Ref Filt="IsRowVector"/>
## or <Ref Filt="IsVectorObj"/> returns <K>true</K>.
## In the former case, <A>vector</A> is a list,
## and <Ref Oper="ImmutableVector"/> returns an immutable object for which
## <Ref Filt="IsRowVector"/> returns <K>true</K> (in particular again a list),
## which is equal to <A>vector</A>,
## and which is in the optimal (concerning space and runtime) representation
## for vectors defined over <A>field</A>,
## provided that the entries of <A>vector</A> lie in <A>field</A>.
## In the latter case, if <A>vector</A> is not in <Ref Filt="IsRowVector"/>,
## <Ref Oper="ImmutableVector"/> returns an immutable object that is equal
## to the result of
## <Ref Oper="ChangedBaseDomain" Label="for a vector object"/>
## when this is called with <A>vector</A> and <A>field</A>.
## 
## This means that vectors obtained by several calls of
## <Ref Oper="ImmutableVector"/> for the same <A>field</A> are compatible
## for fast arithmetic without need for field conversion.
## 
## If the input vector <A>vector</A> is in <Ref Filt="IsRowVector"/>
## then it might change its representation as a side effect
## of this function.
## However, one cannot rely on this side effect.
## Also, if <A>vector</A> is already immutable and the result of
## <Ref Oper="ImmutableVector"/> has the same internal representation as
## <A>vector</A>, the result is not necessarily <E>identical</E> to
## <A>vector</A>.
## 
## If <A>change</A> is <K>true</K>, then <A>vector</A> may be changed to
## become immutable; otherwise it is copied first.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareOperation( "ImmutableVector",[IsObject,IsRowVector]);

#############################################################################
##
#O NumberFFVector( <vec>, <sz> )
##
## <#GAPDoc Label="NumberFFVector">
## <ManSection>
## <Oper Name="NumberFFVector" Arg='vec, sz'/>
##
## <Description>
## returns an integer that gives the position minus one of the finite field row vector
## <A>vec</A> in the sorted list of all row vectors over the field with
## <A>sz</A> elements in the same dimension as <A>vec</A>.
## <Ref Oper="NumberFFVector"/> returns <K>fail</K> if the vector cannot be
## represented over the field with <A>sz</A> elements.
## 
## <Example><![CDATA[
## gap> v:=[0,1,2,0]*Z(3);;
## gap> NumberFFVector(v, 3);
## 21
## gap> NumberFFVector(Zero(v),3);
## 0
## gap> V:=EnumeratorSorted(GF(3)^4);
## <enumerator of ( GF(3)^4 )>
## gap> V[21+1] = v;
## true
## ]]></Example>
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareOperation("NumberFFVector", [IsRowVector,IsPosInt]);

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