You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: ddtTerm.m
    path of file: ./repos/FVTool/Calculus
    
    the code of the file until where you have to start completion: function ddt = ddtTerm(phi, phi_old, dt, BC)
% function ddt = ddtTerm(dt, phi)
% it returns the derivative of phi with respect to time in the vector ddt
% phi is a structure with elements phi.value and phi.Old
% mesh structure is used to map the (phi.value-phi.Old) matrix in the
% ddt vector
%
% SYNOPSIS:
%		ddt = ddtTerm(phi, phi_old, dt, BC)
%
% PARAMETERS:
%
%
% RETURNS:
%
%
% EXAMPLE:
%
% SEE ALSO:
%


    
function ddt = ddtTerm(phi, phi_old, dt, BC)
% function ddt = ddtTerm(dt, phi)
% it returns the derivative of phi with respect to time in the vector ddt
% phi is a structure with elements phi.value and phi.Old
% mesh structure is used to map the (phi.value-phi.Old) matrix in the
% ddt vector
%
% SYNOPSIS:
%		ddt = ddtTerm(phi, phi_old, dt, BC)
%
% PARAMETERS:
%
%
% RETURNS:
%
%
% EXAMPLE:
%
% SEE ALSO:
%


d = phi.domain.dimension;
if (d ==1) || (d==1.5) || (d==1.8)
	ddt = createCellVariable(phi.domain, (phi.value(2:end