RosettaCode Monty Hall - Revision history

Marco2357 at 08:27, 3 October 2012

2012-10-03T08:27:26Z

Marco2357 at 08:27, 3 October 2012

2012-10-03T08:27:12Z

Peter gummer: /* Eiffel code */

2012-08-12T02:40:09Z

‎Eiffel code

Peter gummer: Monty Hall implementation that compiles and runs

2012-08-12T02:38:06Z

Monty Hall implementation that compiles and runs

Peter gummer at 00:15, 10 August 2012

2012-08-10T00:15:42Z

Peter gummer: /* Eiffel code */

2012-08-10T00:14:33Z

‎Eiffel code

Bmeyer at 17:25, 9 August 2012

2012-08-09T17:25:27Z

Bmeyer at 17:24, 9 August 2012

2012-08-09T17:24:14Z

Manus at 17:24, 9 August 2012

2012-08-09T17:24:07Z

Bmeyer: /* Reference */

2012-08-09T17:22:45Z

‎Reference

@@ Line 2: / Line 2: @@
 [[Category:Flash Code ]]
-'''[[RosettaCode]] Overview'''
+'''-> [[RosettaCode]] Overview'''
 ==Reference==

@@ Line 1: / Line 1: @@
 [[Category:Rosetta Code]]
 [[Category:Flash Code ]]
 ==Reference==

← Older revision		Revision as of 02:40, 12 August 2012
Line 11:		Line 11:

	Staying wins 333504 times.		Staying wins 333504 times.
		+
	Switching wins 666496 times.		Switching wins 666496 times.

@@ Line 8: / Line 8: @@
 ==Eiffel code==
-Here's an initial implementation, just to get things started. I just typed this straight into the wiki, so it might not even compile.
+Here's a candidate implementation. This compiles and runs, producing output similar to this:
-Please feel free to edit this in place, I won't be offended.
+Staying wins 333504 times.
 <e>
-class MONTY_HALL
+class
-feature
+create
 	play
 		local
 			doors: ARRAYED_LIST [BOOLEAN]
 			chosen, shown: INTEGER
 		do
-			games := 1000000
+			create doors.make_filled (Door_count)	-- False is a goat, True is a car
-			create random.make
+			doors [next_random_door] := True	-- Put a car behind a random door
-			across 1 |..| games as plays loop
+			-- Monty selects a door which is neither the winner nor the choice
-				create doors.make_filled (3)	-- False is a goat, True is a car
+			from
-				random.forth
+				shown := next_random_door
-				doors [random.item \\ 3 + 1] := True	-- Put a car behind a random door
+			until
 				shown /= chosen and not doors [shown]
-				random.forth
+			loop
-				chosen := random.item \\ 3 + 1	-- Pick a door, any door
+				shown := next_random_door
+			end
-				from shown := chosen until shown /= chosen and not doors [shown] loop
-					random.forth
-					shown := random.item \\ 3 + 1
-				end
-				if doors [chosen] then	-- If you would have won by staying, count it
+			if doors [chosen] then	-- If you would have won by staying, count it
-					stay_wins := stay_wins + 1
+				staying_wins := staying_wins + 1
-				end
 			end
-			out ("Staying wins " + stay_wins + " times.%N")
+feature {NONE} -- Implementation
-			out ("Switching wins " + games - stay_wins + " times.%N")
 		end

← Older revision		Revision as of 00:15, 10 August 2012
Line 53:		Line 53:

	</e>		</e>
−
−	Note that the implementations in many other languages maintain a separate variable to count the number of switch wins. They calculate whether switching wins at each step via some funky logic that relies on zero-based array indexing, which would be inconvenient in Eiffel. But we don't need to do that at all anyway, because calculating it at each step is completely redundant: we can just do a final subtraction at the end, right?

	==Comments==		==Comments==
		+
		+	Note that the implementations in many other languages maintain a separate variable to count the number of switch wins. They calculate whether switching wins at each step via some funky logic that relies on zero-based array indexing, which would be inconvenient in Eiffel. But we don't need to do that at all anyway, because calculating it at each step is completely redundant: we can just do a final subtraction at the end, right?

← Older revision		Revision as of 00:14, 10 August 2012
Line 7:		Line 7:

	==Eiffel code==		==Eiffel code==
		+
		+	Here's an initial implementation, just to get things started. I just typed this straight into the wiki, so it might not even compile.
		+
		+	Please feel free to edit this in place, I won't be offended.
		+
		+	<e>
		+	class MONTY_HALL
		+
		+	feature
		+
		+	play
		+	local
		+	games: INTEGER
		+	random: RANDOM
		+	doors: ARRAYED_LIST [BOOLEAN]
		+	chosen, shown: INTEGER
		+	stayWins: INTEGER
		+	do
		+	games := 1000000
		+	create random.make
		+
		+	across 1 \|..\| games as plays loop
		+	create doors.make_filled (3) -- False is a goat, True is a car
		+	random.forth
		+	doors [random.item \\ 3 + 1] := True -- Put a car behind a random door
		+
		+	random.forth
		+	chosen := random.item \\ 3 + 1 -- Pick a door, any door
		+
		+	from shown := chosen until shown /= chosen and not doors [shown] loop
		+	random.forth
		+	shown := random.item \\ 3 + 1
		+	end
		+
		+	if doors [chosen] then -- If you would have won by staying, count it
		+	stay_wins := stay_wins + 1
		+	end
		+	end
		+
		+	out ("Staying wins " + stay_wins + " times.%N")
		+	out ("Switching wins " + games - stay_wins + " times.%N")
		+	end
		+
		+	end
		+
		+	</e>
		+
		+	Note that the implementations in many other languages maintain a separate variable to count the number of switch wins. They calculate whether switching wins at each step via some funky logic that relies on zero-based array indexing, which would be inconvenient in Eiffel. But we don't need to do that at all anyway, because calculating it at each step is completely redundant: we can just do a final subtraction at the end, right?

	==Comments==		==Comments==

@@ Line 4: / Line 4: @@
 ==Reference==
 Statement of the Monty Hall problem on RosettaCode: [http://rosettacode.org/wiki/Monty_Hall_problem here].
-<p>Deadline for adding to RosettaCode page: 31 Aug 2012; submitter:
+<br>Deadline for adding to RosettaCode page: 31 Aug 2012; submitter:
 ==Eiffel code==
 ==Comments==

← Older revision		Revision as of 17:24, 9 August 2012
Line 7:		Line 7:

	==Eiffel code==		==Eiffel code==
		+
	==Comments==		==Comments==

← Older revision		Revision as of 17:24, 9 August 2012
Line 1:		Line 1:
	[[Category:Rosetta Code]]		[[Category:Rosetta Code]]
		+	[[Category:Flash Code ]]

	==Reference==		==Reference==