How to intersect with any sprite of a certain cast member?

Question

Hi. I am trying to script a simple 2d platformer engine for a larger University project. I have movement sorted with W and A and gravity. I can get collision detection with the floor by doing
if sprite 1 intersects sprite 2 then
     gvGrav = 0
end if
Sprite 1 is the player and sprite 2 is an instance of the cast member called ground. How would I get this to work with any sprite that is ground? Ill paste the full code below.
global gvRight
global gvLeft
global gvGrav
global gvDown
on enterFrame
  -----------MOVE LEFT---------------------
  if keyPressed("a") then
    sprite(4).locH=sprite(4).locH+gvLeft
    _movie.updateStage()
    gvLeft = gvLeft - .5
    if gvLeft < - 15 then
      gvLeft = -15
    end if
  end if
  if not keypressed("a") then
    gvLeft = 0
  end if
  -----------MOVE RIGHT--------------------
  if keyPressed("d") then
    sprite(4).locH=sprite(4).locH+gvRight
    _movie.updateStage()
    gvRight = gvRight + .5
    if gvRight > 15 then
      gvRight = 15
    end if
  end if
  if not keypressed("d") then
    gvRight = 0
  end if 
  -----------GRAVITY-------------------------
  gvGrav = gvGrav
  sprite(4).locV=sprite(4).locV+gvGrav
  _movie.updateStage()
  gvGrav = gvGrav +.5
  if gvGrav > 30 then
    gvGrav = 30
  end if
  -------------GravityCollision----------------------
  if sprite 4 intersects sprite 1 then
    gvGrav = 0
  end if
  if sprite 4 intersects sprite 2 then
    gvGrav = 0
  end if
end if

Answer 1

I dare say there's a better way to do this, but an easy way is to set a global variable, do a sendallsprites message, and check the global variable again.
So, if you had an extra global in your man control script:
global hitman
then in your collision checking part you would say this:
  hitman = false
  sendallsprites #checkcollision 4
  if hitman = true then
    gvGrav = 0
  end if
The #checkcollision message would get sent to all sprites, and if you had a behavior placed on the floor sprites, that was like this:
global hitman
property mysprite
on beginsprite me
  mysprite = the spritenum of me
end
on checkcollision me,s
  if sprite s intersects sprite mysprite then
    hitman = true
  end if
end
any one of those sprites that intersected with the sprite you ask about would then change the global 'hit man' variable to be true. To make a sprite behave like floor, you would just attach that behavior script.
Notice how the floor sprite makes a note of its sprite number when it first shows up on the stage, you could do the same with your other script, if it's attached to the man character. Then you wouldn't have to have it hard coded to '4', which would save some headaches later if you have to change the sprite layers.