Anyone know where to find material's base node source code like panner, dot, cross etc?

hi guys, I just wonder what panner node source code looks like, so I try to find it in the engine source code, and unfortunately I didnt find anything in the materialexpression.cpp, all what I can see is the definition in engine:

UMaterialExpressionPanner::UMaterialExpressionPanner(const FObjectInitializer& ObjectInitializer)
: Super(ObjectInitializer)
// Structure to hold one-time initialization
struct FConstructorStatics
FText NAME_Coordinates;
: NAME_Coordinates(LOCTEXT( “Coordinates”, “Coordinates” ))
static FConstructorStatics ConstructorStatics;

but not something mathmatical how it works. can any one help me on that plz?

Most of the code is in HLSL material translator.