Merge pull request #246 from zickgraf/master

Optimize Preimage
homalg-project · Feb 12, 2024 · e6bb67d · e6bb67d
2 parents 094948d + ad6fab3
commit e6bb67d
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Showing 2 changed files with 4 additions and 6 deletions.
diff --git a/PackageInfo.g b/PackageInfo.g
@@ -10,7 +10,7 @@ SetPackageInfo( rec(
 
 PackageName := "FinSetsForCAP",
 Subtitle := "The elementary topos of (skeletal) finite sets",
-Version := "2024.02-04",
+Version := "2024.02-05",
 
 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",

diff --git a/gap/SkeletalFinSets.gi b/gap/SkeletalFinSets.gi
@@ -132,13 +132,11 @@ InstallMethod( Preimage,
         [ IsMorphismInSkeletalCategoryOfFiniteSets, IsList ],
 
   function ( phi, t )
-    local S;
+    local positions;
 
-    S := AsList( Source( phi ) );
+    positions := PositionsProperty( AsList( phi ), x -> x in t );
 
-    phi := AsList( phi );
-
-    return Filtered( S, i -> phi[1 + i] in t );
+    return List( positions, i -> BigInt( i - 1 ) );
 
 end );