I have expressions like $a - b + c(d-\frac12 e) + \frac{f-i g}{h}$ where $i$ is the imaginary number. I would like to remove all minus signs (and if possible, also get rid of constants such as $\frac12$ or $i$, to obtain $a + b + c(d+e) + \frac{f+g}{h}$.
Is there a way to do this in mathematica? My attempts at defining a suitable replacement rule have not succeeded so far.