June 2018 Update

Task/24-game/Ring/24-game.ring

@@ -0,0 +1,63 @@
+# Project : 24 game
+# Date    : 2018/02/21
+# Author : Gal Zsolt (~ CalmoSoft ~)
+# Email   : <calmosoft@gmail.com>
+
+load "stdlib.ring"
+digits = list(4)
+check = list(4)
+for choice = 1 to 4
+     digits[choice] = random(9)
+next
+
+see "enter an equation (using all of, and only, the single digits " + nl
+for index = 1 to 4
+     see digits[index]
+     if index != 4
+        see " "
+    ok
+next
+see ")"
+see " which evaluates to exactly 24. only multiplication (*), division (/)," + nl
+see "addition (+) & subtraction (-) operations and parentheses are allowed:" + nl
+see "24 = "
+give equation
+see "equation = " + equation + nl
+
+while true
+        for char = 1 to len(equation)
+             digit = substr("0123456789", equation[char]) - 1
+             if digit >= 0
+                for index = 1 to 4
+                     if digit = digits[index]
+                        if not check[index]
+                           check[index] = 1
+                           exit
+                        ok
+                     ok
+                next
+                if index > 4
+                   see "sorry, you used the illegal digit " + digit + nl
+                   exit 2
+                ok
+            ok
+        next
+        for index = 1 to 4
+             if check[index] = 0
+                see "sorry, you failed to use the digit " + digits[index] + nl
+                exit 2
+             ok
+        next
+        for pair = 11 to 99
+             if substr(equation, string(pair))
+                see "sorry, you may not use a pair of digits " + pair + nl
+             ok
+        next
+        eval("result = " + equation)
+        if result = 24
+           see "congratulations, you succeeded in the task!" + nl
+           exit
+        else
+           see "sorry, your equation evaluated to " + result + " rather than 24!" + nl
+        ok
+end