emission is not a member of UnityEngine.ParticleSystem?

i seem to be very confused... because i'm looking at this page and emission is the 5th variable down.

yet any time i try to refer to a particle systems emission module like:

 var ps : ParticleSystem;
 ps.emission;

i get: 'emission' is not a member of 'UnityEngine.ParticleSystem'

how do i go about accessing the emission module of a particle system in code? I'm trying to change the emission type back and forth between distance and time when some conditions are met.

edit: now again i'm trying to:

 lr.SetPositions(points);

where 'points' is an array of Vector3, and 'lr' is a LineRenderer. i get an error saying SetPositions is not a member of LineRenderer even though that function is the 3rd one listed on the api...

im gonna kick myself when i figure this out i bet.