Housekeeping with strings

Hi, so I’m currently writing some code which produces lots of values. It currently loops over with different values for (in this case FL) each time.
I’m trying to get it so it changes the file name to correspond with the double_t FL.
Here is the code in question .

[code]TString FLhistoname= “FLhisto_FLbeing_THISISLONG.pdf”;
TH1F* FLHisto= new TH1F(“FLHisto”, “FLHisto”, 40, (F_L-0.1), (F_L+0.1));

//Set the variables
FLhistoname.ReplaceAll(“THISISLONG”, (F_L) );
FLhistoname.ReplaceAll(" “,”");

//draw histogram
c1 ->Print(FLhisto);[/code]

You’ll note that if I remove the “set the variables” lines ( FLhistoname.ReplaceAll(“THISISLONG”, Form(F_L) );
FLhistoname.ReplaceAll(" “,”"); ) then the code works fine, however if I don’t I get the error.
Error is :

Error: Ambiguous overload resolution (10001,2) /home/ap12019/
Calling : TString::TString(Double_t);
Match rank: file line signature

Putting ftoa in front of the FL has been suggested as a solution but that doesn’t work.
Any help? (I don’t know if this is something to do with C++ or root as this is the first work I’ve done with either.

What about using the TString::Format() helper function of ROOT?