Merge pull request #227 from mohamed-barakat/IsColiftable

fixed IsColiftable

Author: zickgraf

PackageInfo.g

@@ -10,7 +10,7 @@ SetPackageInfo( rec(
 
 PackageName := "FinSetsForCAP",
 Subtitle := "The elementary topos of (skeletal) finite sets",
-Version := "2023.10-01",
+Version := "2023.10-02",
 
 Date := (function ( ) if IsBound( GAPInfo.SystemEnvironment.GAP_PKG_RELEASE_DATE ) then return GAPInfo.SystemEnvironment.GAP_PKG_RELEASE_DATE; else return Concatenation( ~.Version{[ 1 .. 4 ]}, "-", ~.Version{[ 6, 7 ]}, "-01" ); fi; end)( ),
 License := "GPL-2.0-or-later",

examples/SkeletalColift.g

@@ -3,6 +3,14 @@
 #! @Example
 LoadPackage( "FinSetsForCAP", false );
 #! true
+I := InitialObject( SkeletalFinSets );
+#! |0|
+iota := UniversalMorphismIntoTerminalObject( I );
+#! |0| → |1|
+id := IdentityMorphism( I );
+#! |0| → |0|
+IsColiftable( iota, id );
+#! false
 m := FinSet( 5 );
 #! |5|
 n := FinSet( 4 );

gap/SkeletalFinSets.gi

@@ -451,7 +451,12 @@ AddIsColiftable( SkeletalFinSets,
     ff := AsList( f );
     gg := AsList( g );
 
-    return ForAll( Set( ff ), i -> Length( Set( gg{Positions( ff, i )} ) ) = 1 );
+    ## Range( g ) initial implies Range( f ) initial
+    if IsInitial( cat, Range( g ) ) and not IsInitial( cat, Range( f ) ) then
+        return false;
+    else
+        return ForAll( Set( ff ), i -> Length( Set( gg{Positions( ff, i )} ) ) = 1 );
+    fi;
 
 end );
 

gap/precompiled_categories/SkeletalCategoryOfFiniteSetsWithMorphismsGivenByListsPrecompiled.gi

@@ -397,11 +397,16 @@ end
 ########
 function ( cat_1, arg2_1, arg3_1 )
     local hoisted_2_1, deduped_3_1;
-    deduped_3_1 := AsList( arg2_1 );
-    hoisted_2_1 := AsList( arg3_1 );
-    return ForAll( SSortedList( deduped_3_1 ), function ( i_2 )
-            return Length( SSortedList( hoisted_2_1{Positions( deduped_3_1, i_2 )} ) ) = 1;
-        end );
+    if Length( Range( arg3_1 ) ) = 0 and not Length( Range( arg2_1 ) ) = 0 then
+        return false;
+    else
+        deduped_3_1 := AsList( arg2_1 );
+        hoisted_2_1 := AsList( arg3_1 );
+        return ForAll( SSortedList( deduped_3_1 ), function ( i_2 )
+                return Length( SSortedList( hoisted_2_1{Positions( deduped_3_1, i_2 )} ) ) = 1;
+            end );
+    fi;
+    return;
 end
 ########