Thread: does const make functions faster?

Hi,

Usually when I am writing some code, I do not use const (I have now realized that may be I should . So one of my functions could look like this:

Code:

void setSpeed(float NewSpeed) {Speed=NewSpeed;}

Then I just put a const modifier before float NewSpeed:

Code:

void setSpeed(const float NewSpeed) {Speed=NewSpeed;}

I understand that it tells the compiler that NewSpeed will never be changed during the execution of the function. But would it make the function faster? Or: will NewSpeed occupy less memory?

And:

Code:

//will this
float getSpeed() const {return Speed;}

//be faster than this:
float getSpeed() {return Speed;}

What about the 'mutable' modifier? Will it make a function faster? I have really never seen mutable being used in regular code. Why is that?

thnx in advance