[mat_brain]

Hello, everyone.
I'm new to OpenFOAM and i'm trying to make a linear function as a boundary condition, something like

T = 100 - x

I tried this, but it doesn't work:

patch1
{
        type            fixedValue;
	value           #codeStream
	{
		codeInclude	#{
			#include "fvModels.H"
		#};
		codeOptions	#{
			-I$(LIB_SRC)/finiteVolume/lnInclude \
			-I$(LIB_SRC)/meshTools/lnInclude
		#};
		codeLibs	#{
			-lmeshTools \
			-lfiniteVolume
		#};
		code		#{
			const IOdictionary& d = static_cast<const IOdictionary&>(dict.parent().parent());	
			const fvMesh& mesh = refCast<const fvMesh>(d.db());									
			const label id = mesh.boundary().findPatchID("patch1");								
			const fvPatch& patch = mesh.boundary()[id];											
			scalarField T(patch.size(), 0.);													
								
			forAll(T, i)																		
			{
				const scalar x = patch.Cf()[i].x();												
									
				T[i] = 100 - x; 																
			}
								
			writeEntry(os, "", T);
		#};
	};
}

It's probably very simple, but i don't know what's wrong with that.
I'm looking for a cube with 2 faces with fixed values: 100 and 0 and the lateral faces using this function.
Any help is welcome.