Merge pull request #118 from gap-packages/mh/rm-TerminalObject

Remove (Has)InitialObject, (Has)TerminalObject
gap-packages · Jan 5, 2024 · c0e1d63 · c0e1d63
2 parents fa4df59 + cf06620
commit c0e1d63
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Showing 8 changed files with 6 additions and 32 deletions.
diff --git a/doc/Test.xml b/doc/Test.xml
@@ -509,7 +509,6 @@
 <C>IndeterminateDegrees</C><Br/>
 <C>IndeterminatesOfGradedAlgebraPresentation</C><Br/>
 <C>IndeterminatesOfPolynomial</C><Br/>
-<C>InitialObject</C><Br/>
 <C>InnerAutomorphismGroupQuandle</C><Br/>
 <C>InnerAutomorphismGroupQuandleAsPerm</C><Br/>
 <C>InverseRingHomomorphism</C><Br/>
@@ -536,7 +535,6 @@
 <C>SourcePolynomialRing</C><Br/>
 <C>SourceRelations</C><Br/>
 <C>StarGraph</C><Br/>
-<C>TerminalObject</C><Br/>
 <C>TermsOfPolynomial</C><Br/>
 <C>UnivariateMonomialsOfMonomial</C><Br/>
 <C>CoefficientsRing</C><Br/>

diff --git a/doc/Undocumented.xml b/doc/Undocumented.xml
@@ -1766,9 +1766,6 @@
 <C>IndexInSL2O</C>&nbsp;&nbsp;&nbsp;&nbsp;<B>Examples:</B> <URL><Link>../tutorial/chap11.html</Link><LinkText>1</LinkText></URL>&nbsp; 
 <Br/>
 <Br/>
-<C>InitialObject</C>&nbsp;&nbsp;&nbsp;&nbsp;<B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutAbelianCategories.html</Link><LinkText>1</LinkText></URL>&nbsp; 
-<Br/>
-<Br/>
 <C>InnerAutomorphismGroupQuandle</C>&nbsp;&nbsp;&nbsp;&nbsp;<B>Examples:</B> <Br/>
 <Br/>
 <C>InnerAutomorphismGroupQuandleAsPerm</C>&nbsp;&nbsp;&nbsp;&nbsp;<B>Examples:</B> <Br/>
@@ -1848,8 +1845,6 @@
 <Br/>
 <C>StarGraphAttr</C>&nbsp;&nbsp;&nbsp;&nbsp;<B>Examples:</B> <Br/>
 <Br/>
-<C>TerminalObject</C>&nbsp;&nbsp;&nbsp;&nbsp;<B>Examples:</B> <Br/>
-<Br/>
 <C>TermsOfPolynomial</C>&nbsp;&nbsp;&nbsp;&nbsp;<B>Examples:</B> <Br/>
 <Br/>
 <C>UnivariateMonomialsOfMonomial</C>&nbsp;&nbsp;&nbsp;&nbsp;<B>Examples:</B> <Br/>

diff --git a/doc/newCategories.xml b/doc/newCategories.xml
@@ -17,10 +17,6 @@
 </Description> </ManSection> 
 <ManSection> <Func Name="TerminalArrow" Arg="X"/> <Description> <P/> Inputs an object <M>X</M> in some category, and returns the arrow from <M>X</M> to the terminal object in the category. <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutAbelianCategories.html</Link><LinkText>1</LinkText></URL>&nbsp;
 </Description> </ManSection> 
-<ManSection> <Func Name="HasInitialObject" Arg="Name"/> <Description> <P/> Inputs the name of a category and returns true or false depending on whether the category has an initial object. <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutAbelianCategories.html</Link><LinkText>1</LinkText></URL>&nbsp;
-</Description> </ManSection> 
-<ManSection> <Func Name="HasTerminalObject" Arg="Name"/> <Description> <P/> Inputs the name of a category and returns true or false depending on whether the category has a terminal object. <P/><B>Examples:</B> 
-</Description> </ManSection> 
 <ManSection> <Func Name="Source" Arg="f"/> <Description> <P/> Inputs an arrow <M>f</M> in some category, and returns its source. <P/><B>Examples:</B> <URL><Link>../tutorial/chap2.html</Link><LinkText>1</LinkText></URL>&nbsp;, <URL><Link>../tutorial/chap4.html</Link><LinkText>2</LinkText></URL>&nbsp;, <URL><Link>../tutorial/chap7.html</Link><LinkText>3</LinkText></URL>&nbsp;, <URL><Link>../tutorial/chap8.html</Link><LinkText>4</LinkText></URL>&nbsp;, <URL><Link>../www/SideLinks/About/aboutAbelianCategories.html</Link><LinkText>5</LinkText></URL>&nbsp;, <URL><Link>../www/SideLinks/About/aboutNonabelian.html</Link><LinkText>6</LinkText></URL>&nbsp;, <URL><Link>../www/SideLinks/About/aboutCoefficientSequence.html</Link><LinkText>7</LinkText></URL>&nbsp;, <URL><Link>../www/SideLinks/About/aboutCoveringSpaces.html</Link><LinkText>8</LinkText></URL>&nbsp;, <URL><Link>../www/SideLinks/About/aboutCoverinSpaces.html</Link><LinkText>9</LinkText></URL>&nbsp;, <URL><Link>../www/SideLinks/About/aboutFunctorial.html</Link><LinkText>10</LinkText></URL>&nbsp;, <URL><Link>../www/SideLinks/About/aboutLieCovers.html</Link><LinkText>11</LinkText></URL>&nbsp;
 </Description> </ManSection> 
 <ManSection> <Func Name="Target" Arg="f"/> <Description> <P/> Inputs an arrow <M>f</M> in some category, and returns its target. <P/><B>Examples:</B> <URL><Link>../tutorial/chap1.html</Link><LinkText>1</LinkText></URL>&nbsp;, <URL><Link>../tutorial/chap2.html</Link><LinkText>2</LinkText></URL>&nbsp;, <URL><Link>../tutorial/chap7.html</Link><LinkText>3</LinkText></URL>&nbsp;, <URL><Link>../tutorial/chap8.html</Link><LinkText>4</LinkText></URL>&nbsp;, <URL><Link>../www/SideLinks/About/aboutAbelianCategories.html</Link><LinkText>5</LinkText></URL>&nbsp;, <URL><Link>../www/SideLinks/About/aboutCoefficientSequence.html</Link><LinkText>6</LinkText></URL>&nbsp;, <URL><Link>../www/SideLinks/About/aboutCoveringSpaces.html</Link><LinkText>7</LinkText></URL>&nbsp;, <URL><Link>../www/SideLinks/About/aboutCoverinSpaces.html</Link><LinkText>8</LinkText></URL>&nbsp;

diff --git a/lib/CategoryTheory/categories.gd b/lib/CategoryTheory/categories.gd
@@ -174,9 +174,6 @@ DeclareAttribute( "Mapping" ,        IsCategoryArrow );
 ##
 DeclareProperty("IsAbelianCategory", IsString);
 DeclareProperty("IsAdditiveCategory", IsString);
-DeclareAttribute("TerminalObject", IsString); 
-#DeclareProperty("HasTerminalObject", IsString);
-DeclareAttribute("InitialObject", IsString); #changed from Propertry
 DeclareAttribute("Pullbacks", IsString); #changed from Propertry
 DeclareAttribute("Pushouts", IsString); #changed from Propertry
 

diff --git a/lib/CategoryTheory/categories.gdold b/lib/CategoryTheory/categories.gdold
@@ -174,9 +174,6 @@ DeclareAttribute( "Mapping" ,        IsCategoryArrow );
 ##
 DeclareProperty("IsAbelianCategory", IsString);
 DeclareProperty("IsAdditiveCategory", IsString);
-DeclareAttribute("TerminalObject", IsString); 
-#DeclareProperty("HasTerminalObject", IsString);
-DeclareAttribute("InitialObject", IsString); #changed from Propertry
 DeclareAttribute("Pullbacks", IsString); #changed from Propertry
 DeclareAttribute("Pushouts", IsString); #changed from Propertry
 

diff --git a/lib/CategoryTheory/categories.gi b/lib/CategoryTheory/categories.gi
@@ -12,9 +12,7 @@
 ##
 BindGlobal("Category_Of_Groups", Objectify(
            NewType(NewFamily("Category_Of_Groups"),
-                       IsString  and 
-                       HasInitialObject
-		       and HasTerminalObject), []));
+                       IsString), []));
 
 
 #############################################################################
@@ -75,8 +73,8 @@ InstallMethod( InitialArrow,
         if not CategoryName(A)=Category_Of_Groups then
         TryNextMethod(); fi;
 
-	initial:=Group( () );
-	INITIAL:=CategoricalEnrichment(initial,CategoryName(A));
+        initial:=Group( () );
+        INITIAL:=CategoricalEnrichment(initial,CategoryName(A));
         phi:=GroupHomomorphismByFunction(initial,Object(A),
                                              x->Identity(Object(A)));
         return CategoryArrow(INITIAL,A,phi,CategoryName(A));
@@ -99,7 +97,8 @@ InstallMethod( TerminalArrow,
 
         terminal:=Group( () );
         TERMINAL:=CategoricalEnrichment(terminal,CategoryName(A));
-        phi:=GroupHomomorphismByFunction(Object(A), terminal,                                             x->Identity(terminal));
+        phi:=GroupHomomorphismByFunction(Object(A), terminal,
+                                             x->Identity(terminal));
         return CategoryArrow(A,TERMINAL,phi,CategoryName(A));
 
         end);

diff --git a/lib/CategoryTheory/categories.giold b/lib/CategoryTheory/categories.giold
@@ -12,9 +12,7 @@
 ##
 Category_Of_Groups:="Category_Of_Groups";
 HAP_type:= NewType(NewFamily("Category_Of_Groups"),
-                       IsString  and 
-                       HasInitialObject
-		       and HasTerminalObject);
+                       IsString);
 ObjectifyWithAttributes(Category_Of_Groups,HAP_type);
 MakeReadOnlyGlobal("Category_Of_Groups");
 

diff --git a/www/SideLinks/About/aboutAbelianCategories.html b/www/SideLinks/About/aboutAbelianCategories.html
@@ -241,12 +241,6 @@ <h3>&nbsp;Our GAP implementation</h3>
 gap&gt; #The last line is essentially a commutative diagram. The<br>
 gap&gt; #line before it is a diagram which does not commute.<br>
       <br>
-gap&gt; #Suppose that we need to know if PHI belongs to a category<br>
-gap&gt; #in which there is an initial object.<br>
-      <br>
-gap&gt; HasInitialObject(CategoryName(PHI));<br>
-true<br>
-      <br>
 gap&gt; #Suppose we need to know if some power of the endomorphism PHI<br>
 gap&gt; #is equal to the identity<br>
       <br>