Change TMath::Sign for inter types to be a templated T1 Math::Sign(T1, T2)....

Change TMath::Sign for inter types to be a templated T1 Math::Sign(T1, T2). This fixes problem of Sign(1,double(x)) observed in TFormula.
ROOT-7375.
Add also an overload of TMath::Sign for LongDouble

core/base/inc/TMathBase.h

@@ -49,13 +49,12 @@ namespace TMath {
    inline Bool_t   Odd(Long_t a);
 
    // Sign
-   inline Short_t  Sign(Short_t a, Short_t b);
-   inline Int_t    Sign(Int_t a, Int_t b);
-   inline Long_t   Sign(Long_t a, Long_t b);
-   inline Long64_t Sign(Long64_t a, Long64_t b);
+   template<typename T1, typename T2>
+   inline T1 Sign( T1 a, T2 b);
    inline Float_t  Sign(Float_t a, Float_t b);
    inline Double_t Sign(Double_t a, Double_t b);
-
+   inline Double_t Sign(LongDouble_t a, LongDouble_t b);
+   
    // Min, Max of two scalars
    inline Short_t   Min(Short_t a, Short_t b);
    inline UShort_t  Min(UShort_t a, UShort_t b);
@@ -128,17 +127,9 @@ inline LongDouble_t TMath::Abs(LongDouble_t d)
 
 //---- Sign --------------------------------------------------------------------
 
-inline Short_t TMath::Sign(Short_t a, Short_t b)
-{ return (b >= 0) ? Abs(a) : Short_t(-Abs(a)); }
-
-inline Int_t TMath::Sign(Int_t a, Int_t b)
-   { return (b >= 0) ? Abs(a) : -Abs(a); }
-
-inline Long_t TMath::Sign(Long_t a, Long_t b)
-   { return (b >= 0) ? Abs(a) : -Abs(a); }
-
-inline Long64_t TMath::Sign(Long64_t a, Long64_t b)
-   { return (b >= 0) ? Abs(a) : -Abs(a); }
+template<typename T1, typename T2>
+inline T1 TMath::Sign( T1 a, T2 b)
+   { return (b >= 0) ? Abs(a) : -Abs(a); } 
 
 inline Float_t TMath::Sign(Float_t a, Float_t b)
    { return std::copysign(a,b);  }
@@ -146,6 +137,10 @@ inline Float_t TMath::Sign(Float_t a, Float_t b)
 inline Double_t TMath::Sign(Double_t a, Double_t b)
    { return std::copysign(a,b);  }
 
+inline Double_t TMath::Sign(LongDouble_t a, LongDouble_t b)
+   { return std::copysign(a,b);  }
+
+
 //---- Min ---------------------------------------------------------------------
 
 inline Short_t TMath::Min(Short_t a, Short_t b)

test/TFormulaParsingTests.h

@@ -425,8 +425,13 @@ bool test26() {
    ok &= (f.Eval(2) == 2);
    ok &= (f.Eval(-1) == -1);
    ok &= (f.Eval(-3) == 3);
+   TF1 f2("f2","x*TMath::Sign(1,x+2)");
+   ok &= (f2.Eval(2) == 2);
+   ok &= (f2.Eval(-1) == -1);
+   ok &= (f2.Eval(-3) == 3);
    return ok;
 }
+
 bool test27() {
    // test ssq function
    bool ok = true;