A simple script that can convert MATLAB symbolic expression to C implementation.

sym2cpp.m

function [] = sym2cpp( expr, filename, output_size, n_digits )
%SYM2CPP Summary of this function goes here
%   Detailed explanation goes here

if ~exist('n_digits', 'var')
  n_digits = 64;
end

[dim1, dim2] = size(expr);

% This only works for simple expression.
% Need a REAL parser when it get too complicated.
pattern_hat2power = '([^()*/+-]*)\^([^()*/+-]*)';
tmpl = get_template;

expr_64 = vpa(expr, n_digits);

expr_str = '';
for i = 1:dim1
    for j = 1:dim2
        s = char(expr_64(i, j));
        s = regexprep(s, pattern_hat2power, 'pow($1, $2)');
        
        % MATLAB use Fortran, and Fortran is column-major.
        idx = (j-1) * dim1 + (i-1);
        s = sprintf('    output[%2d] = %s;\n', idx, s);
        expr_str = [expr_str, s];
    end
end

codes = sprintf(tmpl, expr_str, output_size(1), output_size(2));

c_fn = [filename, '.c'];

fid = fopen(c_fn, 'w');
fprintf(fid, codes);
fclose(fid);

mex(c_fn);

end

function [tmpl] = get_template()

tmpl = ['#include "mex.h"\n', ...
'\n', ...
'#define theta_1 theta[0]\n', ... % This is for my KDC project
'#define theta_2 theta[1]\n', ...
'#define theta_3 theta[2]\n', ...
'#define theta_4 theta[3]\n', ...
'#define theta_5 theta[4]\n', ...
'#define theta_6 theta[5]\n', ...
'#define omega_1 omega[0]\n', ...
'#define omega_2 omega[1]\n', ...
'#define omega_3 omega[2]\n', ...
'#define omega_4 omega[3]\n', ...
'#define omega_5 omega[4]\n', ...
'#define omega_6 omega[5]\n', ...
'\n', ...
'void compute(double output[], double theta[], double omega[]) {\n%s}', ...
'\n\n', ...
'void mexFunction( int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[] ) {\n', ...
'    size_t rows = %d, cols = %d;\n', ...
'    plhs[0] = mxCreateDoubleMatrix((mwSize) rows, (mwSize) cols, mxREAL);\n', ...
'    double* output = mxGetPr(plhs[0]);\n', ...
'    double* theta = mxGetPr(prhs[0]);\n', ...
'    double* omega = mxGetPr(prhs[1]);\n', ...
'    compute(output, theta, omega);\n', ...
'}'];

end