Introduce kernel-level LCM_INT

This is done using the gmp function mpz_lcm.
gap-system · Dec 12, 2017 · 33ec3d6 · 33ec3d6
1 parent 9ae06ac
commit 33ec3d6
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Showing 2 changed files with 39 additions and 7 deletions.
diff --git a/lib/integer.gi b/lib/integer.gi
@@ -1078,13 +1078,7 @@ InstallGlobalFunction( IsPrimePowerInt,
 ##
 #F  LcmInt( <m>, <n> )  . . . . . . . . . . least common multiple of integers
 ##
-InstallGlobalFunction(LcmInt,function ( n, m )
-    if m = 0  and n = 0  then
-        return 0;
-    else
-        return AbsInt( m / GcdInt( m, n ) * n );
-    fi;
-end);
+InstallGlobalFunction(LcmInt, LCM_INT);
 
 
 #############################################################################

diff --git a/src/integer.c b/src/integer.c
@@ -2202,6 +2202,43 @@ Obj FuncGCD_INT ( Obj self, Obj opL, Obj opR )
   return GcdInt( opL, opR );
 }
 
+Obj LcmInt ( Obj opL, Obj opR )
+{
+    UInt sizeL, sizeR;
+    fake_mpz_t mpzL, mpzR, mpzResult;
+    Obj result;
+
+    CHECK_INT(opL);
+    CHECK_INT(opR);
+
+    if (opL == INTOBJ_INT(0)) return AbsInt(opR);
+    if (opR == INTOBJ_INT(0)) return AbsInt(opL);
+
+    sizeL = SIZE_INT_OR_INTOBJ(opL);
+    sizeR = SIZE_INT_OR_INTOBJ(opR);
+
+    NEW_FAKEMPZ( mpzResult, sizeL + sizeR );
+    FAKEMPZ_GMPorINTOBJ( mpzL, opL );
+    FAKEMPZ_GMPorINTOBJ( mpzR, opR );
+
+    /* compute the gcd */
+    mpz_lcm( MPZ_FAKEMPZ(mpzResult), MPZ_FAKEMPZ(mpzL), MPZ_FAKEMPZ(mpzR) );
+
+    /* convert result to GAP object and return it */
+    CHECK_FAKEMPZ(mpzResult);
+    CHECK_FAKEMPZ(mpzL);
+    CHECK_FAKEMPZ(mpzR);
+    result = GMPorINTOBJ_FAKEMPZ( mpzResult );
+    CHECK_INT(result);
+    return result;
+}
+
+Obj FuncLCM_INT( Obj self, Obj opL, Obj opR )
+{
+    REQUIRE_INT_ARG( "LcmInt", "left", opL );
+    REQUIRE_INT_ARG( "LcmInt", "right", opR );
+    return LcmInt( opL, opR );
+}
 
 /****************************************************************************
 **
@@ -2621,6 +2658,7 @@ static StructGVarFunc GVarFuncs [] = {
   GVAR_FUNC(SIGN_INT, 1, "x"),
   GVAR_FUNC(REM_INT, 2, "gmp1, gmp2"),
   GVAR_FUNC(GCD_INT, 2, "gmp1, gmp2"),
+  GVAR_FUNC(LCM_INT, 2, "gmp1, gmp2"),
   GVAR_FUNC(PROD_INT_OBJ, 2, "gmp, obj"),
   GVAR_FUNC(POW_OBJ_INT, 2, "obj, gmp"),
   GVAR_FUNC(JACOBI_INT, 2, "n, m"),