Data commit

Task/24-game/Julia/24-game.julia

@@ -0,0 +1,28 @@
+validexpr(ex::Expr) = ex.head == :call && ex.args[1] in [:*,:/,:+,:-] && all(validexpr, ex.args[2:end])
+validexpr(ex::Int) = true
+validexpr(ex::Any) = false
+findnumbers(ex::Number) = Int[ex]
+findnumbers(ex::Expr) = vcat(map(findnumbers, ex.args)...)
+findnumbers(ex::Any) = Int[]
+function twentyfour()
+    digits = sort!(rand(1:9, 4))
+    while true
+        print("enter expression using $digits => ")
+        ex = parse(readline())
+        try
+            validexpr(ex) || error("only *, /, +, - of integers is allowed")
+            nums = sort!(findnumbers(ex))
+            nums == digits || error("expression $ex used numbers $nums != $digits")
+            val = eval(ex)
+            val == 24 || error("expression $ex evaluated to $val, not 24")
+            println("you won!")
+            return
+        catch e
+            if isa(e, ErrorException)
+                println("incorrect: ", e.msg)
+            else
+                rethrow()
+            end
+        end
+    end
+end