some guidelines to authors of matlab/octave code so it is easier to convert it to C/C++

matlab-to-cpp-guideleines.md

matlab/octave and C++

1. use parentheses around “if” conditions

good:

if (x = y && (x + y > 3))

not good:

if x = y && (x + y > 3)

2. initialize variables and don’t assume zeros

good:

x = 0;
if (a > 0)
  x = 1;
end
% at this point x is either 0 or 1

not good:

if (a > 0)
  x = 1;
end
% at this point x is either 0 or 1

3. matlab variables don’t have scope, create artificial scope for them and don’t reuse them

good:

% this is not needed, but indicate the “scope” of “some_variable”
some_variable = 0
for i = 1 : 100 
  if (x > 0)
   some_variable = 10;
  else
    some_variable = 0;
  end %if
end %for sample
…
for i = 1 : 100 
  if (some_variable == 10)
  … 
  end %if
end %for i

not good:

some_variable = 0
for i = 1 : 100 
  if (x > 0)
   some_variable = 10;
  else
    some_variable = 0;
  end %if
end %for sample
…
for i = 1 : 100 
  if (some_variable == 10)
  … 
  end %if
end %for i

4. don’t create arrays just to perform matrix operations on them (although this is the preferred way of doing that in matlab):

good:

for sample = 1 : 100
  sum_x = sum_x + rand();
end
avg_x = sum_x/100;

not good:

for sample = 1 : 100
  x(sample) = rand();
end
avg_x = mean(x);

5. use assert when things must not happen (this finds lots of programming bugs and help understand the software). Also, try to make sure there is always an “else” section to an if..elseif statement:

% f() should not return negatives
x = f();

if (x == 0)
  do_something
elseif (x > 0)
  do_something_else
else
  assert(0);
end

6. don’t optimize using copy&paste. use functions instead

good:

function f(is_x_positive)
  … 
  % 100 lines of code + some logic on is_x_zero
end
…

if (x == 0)
  f(1);
else
  f(0);
end % if 

not good:

if (x == 0)
  …
  % 100 lines of code
else
  …
  % very similar 100 lines of code
end % if 

7. don’t use very long lines, use “...” instead (works for both matlab and octave). Putting comments is different lines than code also help with that

8. make sure indentation is correct, not too much, not too little

good:

if (x == 0)
  do_something

not good:

if (x == 0)
Do_something

9. (you already do this) indicate which statement the “end” ends:

for sample = 1 : 100 
  if (x > 0)
  … 
  end %if
end %for sample

10. extra parentheses around “^” (power) operator

good:

x = x + (y^(z+1));

not good:

x = x + y^(z+1);

11. named indexes. use “constants” instead of numbers:

good:

MARRIED = 3;
...
prob_of_emp = women(idx, MARRIED);

not good:

prob_of_emp = women(idx, 3);

12. C/matlab style arrays: matlab start from one, C start from zero. try to be consistent with these. when not possible, use another variables and comments. for example:

good:

for interval = 1 : 100
  % the first interval start at t=0
  t = interval - 1;
  x = f(t); 
  y(interval) = x; 
end

not good:

for t = 0 : 100
  x = f(t); 
  y(t+1) = x; 
end

13. variable names and “constants”: matlab does not have “constants”, so try to use: UPPER_CASE for constants and lower_case for non-constants