-- card: 6294 from stack: in
-- bmap block id: 6531
-- flags: 0000
-- background id: 2696
-- name: Expressions
----- HyperTalk script -----
on openCard
  -- put insertion point at beginning of field
  unlock screen
  select before char 1 of card field "Input"
  pass openCard
end openCard

on closeCard
  lock screen
  put empty into card field "Input"
  put empty into card field "Input2"
  pass closeCard
end closeCard


-- "Cleans up" a mathematical expression
-- Remove illegal characters from expression
-- Skips any characters specified as "allowable"
-- Replace x and ÷ with what HyperCard wants
function cleanExpr expr, allowable
put "0123456789" into numeric
put 1 into c
repeat until c > the number of chars in expr
  put char c of expr into ch
  if ch is in allowable then
    add 1 to c
  else
    if ch is in " 0123456789.+-*x/÷^()" then
      if ch = "x" then
        put "*" into char c of expr
      else if ch = "÷" then
        put "/" into char c of expr
      end if
      add 1 to c
    else  -- invalid character: delete it
      delete char c of expr
    end if
  end if
end repeat
if expr is empty then return 0
else return expr
end cleanExpr


-- Compare two expressions of one variable (x)
-- Returns true if they are equivalent
function equivalent expr1, expr2
put cleanExpr(expr1,"x") into expr1
put cleanExpr(expr2,"x") into expr2
put true into match
-- check twice to make sure we don't get a fluke match
repeat 2 times
  put random(999) into x
  if the value of expr1 ≠ the value of expr2
  then put false into match
end repeat
return match
end equivalent





-- part 1 (field)
-- low flags: 01
-- high flags: 0000
-- rect: left=23 top=65 right=106 bottom=245
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 3
-- text size: 14
-- style flags: 0
-- line height: 18
-- part name: 


-- part 3 (field)
-- low flags: 02
-- high flags: 0002
-- rect: left=66 top=116 right=134 bottom=196
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 0
-- text size: 12
-- style flags: 0
-- line height: 16
-- part name: Input
----- HyperTalk script -----
on returnInField
  if the value of cleanExpr(me,"") is 35.70 then rightSound
  else
    wrongSound
    select line 1 of me
  end if
end returnInField



-- part 4 (field)
-- low flags: 00
-- high flags: 0000
-- rect: left=26 top=165 right=206 bottom=248
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 3
-- text size: 14
-- style flags: 0
-- line height: 18
-- part name: 


-- part 5 (field)
-- low flags: 00
-- high flags: 0000
-- rect: left=43 top=227 right=245 bottom=216
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 0
-- text size: 12
-- style flags: 0
-- line height: 16
-- part name: 


-- part 7 (field)
-- low flags: 02
-- high flags: 0000
-- rect: left=69 top=251 right=269 bottom=244
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 0
-- text size: 12
-- style flags: 0
-- line height: 16
-- part name: Input2
----- HyperTalk script -----
on returnInField
  if equivalent(me, "3*x + 2*(12*x + 4)") then rightSound
  else
    wrongSound
    select line 1 of me
  end if
end returnInField



-- part 8 (field)
-- low flags: 00
-- high flags: 0000
-- rect: left=43 top=251 right=269 bottom=70
-- title width / last selected line: 0
-- icon id / first selected line: 0 / 0
-- text alignment: 0
-- font id: 0
-- text size: 12
-- style flags: 0
-- line height: 16
-- part name: 


-- part 9 (button)
-- low flags: 00
-- high flags: 2001
-- rect: left=490 top=320 right=342 bottom=512
-- title width / last selected line: 0
-- icon id / first selected line: 26635 / 26635
-- text alignment: 1
-- font id: 0
-- text size: 12
-- style flags: 0
-- line height: 16
-- part name: 
----- HyperTalk script -----
on mouseUp
  info
end mouseUp



-- part 10 (field)
-- low flags: 81
-- high flags: 2004
-- rect: left=267 top=83 right=287 bottom=504
-- 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: Info
----- HyperTalk script -----
on mouseUp
  info
end mouseUp


-- part contents for card part 1
----- text -----
A $42 shirt is on sale for 15% off.  What is the new price?

-- part contents for card part 4
----- text -----
Enter another form of the following equation.

-- part contents for card part 5
----- text -----
y = 3*x + 2*(12x + 4)

-- part contents for card part 8
----- text -----
y =

-- part contents for card part 10
----- text -----
Note that you can type ANY expression for the shirt price:
  35.7
  42 - .15 * 42
  35 + .7
And you can type ANY equivalent equation.

This is because the answers are evaluated numerically before any matching is done.  (See the scripts for details.)