TFormula is valid

ROOT
1

Hello, I’ve tried to look at the documentation, but I cannot find a way to check if a TFormula is valid or not. Is there a method to do that?

2

What do you mean by “valid” ? syntactically ?

3

yes

4

It looks like “Compile()” does the job:

root [1] TFormula f1("f1","x*x") 
root [2] f1.Compile();
root [4] printf("%d\n",f1.Compile());
0
root [5] TFormula f2("f2","si(x)") 
Error in <TFormula::Compile>:  Bad numerical expression : "si(x)"
root [6] printf("%d\n",f2.Compile());
Error in <TFormula::Compile>:  Bad numerical expression : "si(x)"
1
root [7]
5

is the compilation lazy? I mean if I call it manually then it is redone?

[quote=“couet”]It looks like “Compile()” does the job:

root [1] TFormula f1("f1","x*x") root [2] f1.Compile(); root [4] printf("%d\n",f1.Compile()); 0 root [5] TFormula f2("f2","si(x)") Error in <TFormula::Compile>: Bad numerical expression : "si(x)" root [6] printf("%d\n",f2.Compile()); Error in <TFormula::Compile>: Bad numerical expression : "si(x)" 1 root [7] [/quote]

6

I guess it is… just try.

7

Hi,

Im using ROOT v6.02/12. I tried:

and also:

And both compile, If I call:

form.Compile() or

I get zero, despite these formulae are wrong, also If I evaluate, they do evaluate, however the wrong part (Sin(x[1]) or Tin(x[1]) ) evaluates to one. Why does it happen? I want to put a “if” somewhere that alerts me of a nonsensical function introduced by mistake, before I evaluate and get wrong results. But that “if” would not work here which makes this a very dangerous piece of code.

8

Hi,

You should upgrade ROOT to the latest version, 6.04.06 and use the new TFormula based on Cling, which will compile the expression using a real compiler.

Lorenzo

9

Hi,

Yes, I tried it and it works in ROOT 6.04/06.

Thanks.