introducing an if statement in a solver
 

Hi Foamers!
I want to make a if statement with < and > :
if ( a> ...)

do...
else
do...
but the error is concerned about "<" and ">" and value which I introduced for comparison :a> 0 (the zero)! how come?
I am doing this in the .C of my solver.

the last part of the error is :
' Foam:: tmp<Foam::GeomtericField<double, Foam::fvpatchField, Foam::volMesh> >' is not derived from 'const Foam::Pair <Type>'
Regards Sina