I'm looking for some explanation about vec_length cause the manual is not than clear.

I try to make ma character react in a different way if the other character is benind him in the X axis but when I try with vec_length it doesn't work, the character didn't detec the instruction.

vec_length (play1.x);
vec_length(play2.x);


if (play1.x<play2.x)

{ ...

did i misunderstand the function of vec_length ? do you have some example ?
Do I've to try with c_trace?

Thanks for your help