ID:2189086
 
Example code:
for(var/mob/M in obounds(32))
if(M in left())
// something
if(M in right())
// something
// etc


Problem description:
I'd like all atoms within range to have an effect applied to them, changing it based on whether they are to the left or right of the mob, and their Y value does not matter so long as it is within a certain range of the users.

So, a player 86 pixels to the left and 32 pixels up relative to the user will be effected, as will a player 23 pixels to the right and 12 pixels down relative to the user.

I simply have no clue where to begin and would like help.

If you're using Forum_account's Sidescroller library, you can just compare px, which is your pixel x coordinate on the map. You might also want to add half width to compare centers instead of the left edges.
var cx = px + pwidth / 2
for(var/mob/M in obounds(32))
if(cx > M.px + M.pwidth / 2)
// M is to your left
else
// M is to your right

If you're not using Forum_account's Sidescroller library, and you're using pixel movement, you can still compare relative positions, but using the built-in variables:
if(x * TILE_WIDTH + step_x + bound_x > M.x * TILE_WIDTH + M.step_x + M.bound_x)
// M is to your left
else
// M is to your right

If you're not using pixel movement at all, then you only have to compare x.
In response to Kaiochao
Thanks, I am using Forum_account's sidescroller library :p.