function y = calculate(x)
% Search in the code replacement library for replacement
% and use replacement function if available
% Error if not found
  coder.replace('-errorifnoreplacement');
  y = sqrt(x);
end

function out = top_function(in)
  p = calculate(in);
  out = exp(p);
end

hLib = RTW.TflTable;

%---------- entry: calculate ----------- 
hEnt = RTW.TflCFunctionEntry;
setTflCFunctionEntryParameters(hEnt, ...
  'Key', 'calculate', ...
  'Priority', 100, ...
  'ArrayLayout', 'COLUMN_MAJOR', ...
  'ImplementationName', ...
  'replacement_calculate_impl', ...
  'ImplementationHeaderFile', ...
  'replacement_calculate_impl.h', ...
  'ImplementationSourceFile', ...
  'replacement_calculate_impl.c')
% Conceptual Args

arg = getTflArgFromString(hEnt, 'y1','double');
arg.IOType = 'RTW_IO_OUTPUT';
addConceptualArg(hEnt, arg);

arg = getTflArgFromString(hEnt, 'u1','double');
addConceptualArg(hEnt, arg);

% Implementation Args 

arg = getTflArgFromString(hEnt, 'y1','double');
arg.IOType = 'RTW_IO_OUTPUT';
hEnt.Implementation.setReturn(arg); 

arg = getTflArgFromString(hEnt, 'u1','double');
hEnt.Implementation.addArgument(arg);

addEntry(hLib, hEnt);

function rtwTargetInfo(tr)
% rtwTargetInfo function to register a code 
% replacement library (CRL) 
% for use with codegen

  % Register the CRL defined in local function locCrlRegFcn
  tr.registerTargetInfo(@locCrlRegFcn);

end % End of RTWTARGETINFO

function thisCrl = locCrlRegFcn

  % Instantiate a CRL registry entry
  thisCrl = RTW.TflRegistry;

  % Define the CRL properties
  thisCrl.Name = 'My calculate Example'; 
  thisCrl.Description = 'Demonstration of function replacement';
  thisCrl.TableList = {'crl_table_calculate'};
  thisCrl.BaseTfl = 'C89/C90 (ANSI)';
  thisCrl.TargetHWDeviceType = {'*'};

end % End of LOCCRLREGFCN

RTW.TargetRegistry.getInstance('reset'); 

real_T top_function(real_T in)
{
  real_T p;
  p = replacement_calculate_impl(in);
  return exp(p);
}