-- card: 13170 from stack: in
-- bmap block id: 23687
-- flags: 4000
-- background id: 8367
-- name: Forward Chaining
----- HyperTalk script -----
on openCard
  global cardWait
  put 0 into cardWait
end openCard

on idle
  global cardWait
  if cardWait=13
  then exit idle
  wait 1 seconds
  put cardWait+1 into cardWait
  if cardWait=12
  then send cardStuff to this card
end idle

on cardStuff
  play "harpsichord" "c"
  put "Key is in ignition" into line 1 of card field "A2"
  wait 1 seconds
  play "harpsichord" "e"
  put "Gas gauge is empty" into line 2 of card field "A2"
  wait 1 seconds
  play "harpsichord" "g"
  put "No gas in car" into card field "C2"
  play "boing"
  choose eraser tool
  drag from 155,239 to 341,243
  choose line tool
  set the linesize to 1
  drag from 155,239 to 341,243
  drag from 341,243 to 336,238
  drag from 341,243 to 336,248
  choose browse tool
  play "harpsichord" "c"
  put "The sky is clear" into line 1 of card field "A1"
  play "harpsichord" "g"
  put "No gas in car" into line 2 of card field "A1"
  play "harpsichord" "c5"
  put "Take a walk" into card field "C1"
  show card field "Comments"
end cardStuff

on closeCard
  put empty into card field "A1"
  put empty into card field "C1"
  put empty into card field "A2"
  put empty into card field "C2"
  choose eraser tool
  drag from 155,239 to 341,243
  choose line tool
  set the linesize to 2
  drag from 214,231 to 214,249
  set the linesize to 1
  drag from 290,234 to 290,252
  choose browse tool
  hide card field "Comments"
end closeCard





-- part 1 (field)
-- low flags: 01
-- high flags: 0001
-- rect: left=24 top=76 right=184 bottom=490
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 3
-- text size: 14
-- style flags: 256
-- line height: 18
-- part name: 


-- part 2 (field)
-- low flags: 01
-- high flags: 0000
-- rect: left=39 top=190 right=214 bottom=64
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 3
-- text size: 14
-- style flags: 16640
-- line height: 18
-- part name: 


-- part 3 (field)
-- low flags: 01
-- high flags: 0000
-- rect: left=11 top=225 right=247 bottom=63
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 3
-- text size: 14
-- style flags: 16640
-- line height: 18
-- part name: 


-- part 4 (field)
-- low flags: 01
-- high flags: 0000
-- rect: left=65 top=192 right=227 bottom=214
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 3
-- text size: 12
-- style flags: 0
-- line height: 16
-- part name: A2


-- part 5 (field)
-- low flags: 01
-- high flags: 0000
-- rect: left=64 top=228 right=247 bottom=213
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 3
-- text size: 12
-- style flags: 0
-- line height: 16
-- part name: C2


-- part 6 (field)
-- low flags: 01
-- high flags: 0000
-- rect: left=320 top=216 right=237 bottom=344
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 3
-- text size: 14
-- style flags: 16640
-- line height: 18
-- part name: 


-- part 7 (field)
-- low flags: 01
-- high flags: 0000
-- rect: left=292 top=250 right=272 bottom=344
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 3
-- text size: 14
-- style flags: 16640
-- line height: 18
-- part name: 


-- part 8 (field)
-- low flags: 01
-- high flags: 0000
-- rect: left=344 top=217 right=252 bottom=493
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 3
-- text size: 12
-- style flags: 0
-- line height: 16
-- part name: A1


-- part 9 (field)
-- low flags: 01
-- high flags: 0000
-- rect: left=344 top=252 right=271 bottom=493
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 3
-- text size: 12
-- style flags: 0
-- line height: 16
-- part name: C1


-- part 11 (field)
-- low flags: 81
-- high flags: 0001
-- rect: left=10 top=279 right=336 bottom=381
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 3
-- text size: 14
-- style flags: 256
-- line height: 18
-- part name: Comments


-- part contents for background part 1
----- text -----
Forward Chaining

-- part contents for card part 1
----- text -----
The inference engine in HyperX also uses one other strategy to find Rules to test, called forward chaining. When a Conclusion is reached, HyperX will look the other way for an untested Rule with that Conclusion in it's list of Assertions and add it to the Goal Trail of Rules to be tested.


-- part contents for card part 2
----- text -----
If:

-- part contents for card part 3
----- text -----
Then:

-- part contents for card part 6
----- text -----
If:

-- part contents for card part 7
----- text -----
Then:

-- part contents for card part 11
----- text -----
The same Conclusion was reached as in the backward chaining example, but the Rules were tested in the opposite order.