Fixed GTX_multiple for negative values, issue #51

glm/gtx/multiple.hpp

@@ -51,15 +51,25 @@ namespace glm
 	/// @addtogroup gtx_multiple
 	/// @{
 
-	//! Higher Multiple number of Source.
-	//! From GLM_GTX_multiple extension.
+	/// Higher multiple number of Source.
+	///
+	/// @tparam genType Floating-point or integer scalar or vector types.
+	/// @param Source 
+	/// @param Multiple Must be a null or positive value
+	///
+	/// @see gtx_multiple
 	template <typename genType>
 	genType higherMultiple(
 		genType const & Source,
 		genType const & Multiple);
 
-	//! Lower Multiple number of Source.
-	//! From GLM_GTX_multiple extension.
+	/// Lower multiple number of Source.
+	///
+	/// @tparam genType Floating-point or integer scalar or vector types.
+	/// @param Source 
+	/// @param Multiple Must be a null or positive value
+	///
+	/// @see gtx_multiple
 	template <typename genType>
 	genType lowerMultiple(
 		genType const & Source,

glm/gtx/multiple.inl

@@ -22,8 +22,13 @@ namespace glm
 		genType const & Multiple
 	)
 	{
-		genType Tmp = Source % Multiple;
-		return Tmp ? Source + Multiple - Tmp : Source;
+		assert(genType(0) <= Multiple);
+	
+		genType SourceSign = sign(Source);
+		genType SourceAbs = abs(Source);
+	
+		genType Tmp = SourceAbs % Multiple;
+		return (Tmp ? SourceAbs + Multiple - Tmp : SourceAbs) * SourceSign;
 	}
 
 	template <>
@@ -36,8 +41,14 @@ namespace glm
 		float Source = SourceH.toFloat();
 		float Multiple = MultipleH.toFloat();
 
-		int Tmp = int(float(Source)) % int(Multiple);
-		return detail::half(Tmp ? Source + Multiple - float(Tmp) : Source);
+		assert(float(0) <= Multiple);
+
+		float SourceSign = sign(Source);
+		float SourceAbs = abs(Source);
+
+		int Tmp = int(float(SourceAbs)) % int(Multiple);
+		return detail::half(
+			(Tmp ? SourceAbs + Multiple - float(Tmp) : SourceAbs) * SourceSign);
 	}
 
 	template <>
@@ -47,8 +58,13 @@ namespace glm
 		float const & Multiple
 	)
 	{
-		int Tmp = int(Source) % int(Multiple);
-		return Tmp ? Source + Multiple - float(Tmp) : Source;
+		assert(float(0) <= Multiple);
+	
+		float SourceSign = sign(Source);
+		float SourceAbs = abs(Source);
+				
+		int Tmp = int(SourceAbs) % int(Multiple);
+		return (Tmp ? SourceAbs + Multiple - float(Tmp) : SourceAbs) * SourceSign;
 	}
 
 	template <>
@@ -58,8 +74,13 @@ namespace glm
 		double const & Multiple
 	)
 	{
-		long Tmp = long(Source) % long(Multiple);
-		return Tmp ? Source + Multiple - double(Tmp) : Source;
+		assert(double(0) <= Multiple);
+
+		double SourceSign = sign(Source);
+		double SourceAbs = abs(Source);
+
+		long Tmp = long(SourceAbs) % long(Multiple);
+		return (Tmp ? SourceAbs + Multiple - double(Tmp) : SourceAbs) * SourceSign;
 	}
 
 	VECTORIZE_VEC_VEC(higherMultiple)
@@ -88,6 +109,8 @@ namespace glm
 		float Source = SourceH.toFloat();
 		float Multiple = MultipleH.toFloat();
 
+		assert(float(0) <= Multiple);
+
 		int Tmp = int(float(Source)) % int(float(Multiple));
 		return detail::half(Tmp ? Source - float(Tmp) : Source);
 	}
@@ -99,6 +122,8 @@ namespace glm
 		float const & Multiple
 	)
 	{
+		assert(float(0) <= Multiple);
+	
 		int Tmp = int(Source) % int(Multiple);
 		return Tmp ? Source - float(Tmp) : Source;
 	}
@@ -110,6 +135,8 @@ namespace glm
 		double const & Multiple
 	)
 	{
+		assert(double(0) <= Multiple);
+	
 		long Tmp = long(Source) % long(Multiple);
 		return Tmp ? Source - double(Tmp) : Source;
 	}

readme.txt

@@ -47,6 +47,7 @@ GLM 0.9.5.0: 2013-XX-XX
 - Added rotation function to GTX_quaternion (#22)
 - Added precision variation of each type
 - Added quaternion comparison functions
+- Fixed GTX_multiple for negative value
 
 ================================================================================
 GLM 0.9.4.3: 2013-03-20

test/gtx/gtx_multiple.cpp

@@ -15,12 +15,19 @@ int test_higher()
 	int Error(0);
 
 	int Higher0 = glm::higherMultiple(-5, 4);
-	Error += Higher0 == -4 ? 0 : 1;
-	Error += glm::higherMultiple(-4, 4) == -4 ? 0 : 1;
-	Error += glm::higherMultiple(-3, 4) == -4 ? 0 : 1;
-	Error += glm::higherMultiple(-2, 4) == -4 ? 0 : 1;
-	Error += glm::higherMultiple(-1, 4) == -4 ? 0 : 1;
+	Error += Higher0 == -8 ? 0 : 1;
+	int Higher1 = glm::higherMultiple(-4, 4);
+	Error += Higher1 == -4 ? 0 : 1;
+	int Higher2 = glm::higherMultiple(-3, 4);
+	Error += Higher2 == -4 ? 0 : 1;
+	int Higher3 = glm::higherMultiple(-2, 4);
+	Error += Higher3 == -4 ? 0 : 1;
+	int Higher4 = glm::higherMultiple(-1, 4);
+	Error += Higher4 == -4 ? 0 : 1;
 	Error += glm::higherMultiple(0, 4) == 0 ? 0 : 1;
+	Error += glm::higherMultiple(1, 4) == 4 ? 0 : 1;
+	Error += glm::higherMultiple(2, 4) == 4 ? 0 : 1;
+	Error += glm::higherMultiple(3, 4) == 4 ? 0 : 1;
 	Error += glm::higherMultiple(4, 4) == 4 ? 0 : 1;
 	Error += glm::higherMultiple(5, 4) == 8 ? 0 : 1;
 	Error += glm::higherMultiple(6, 4) == 8 ? 0 : 1;