module ForthTests open FsUnit.Xunit open Xunit open Forth [] let ``Parsing and numbers - numbers just get pushed onto the stack`` () = let expected = Some [1; 2; 3; 4; 5] evaluate ["1 2 3 4 5"] |> should equal expected [] let ``Parsing and numbers - pushes negative numbers onto the stack`` () = let expected = Some [-1; -2; -3; -4; -5] evaluate ["-1 -2 -3 -4 -5"] |> should equal expected [] let ``Addition - can add two numbers`` () = let expected = Some [3] evaluate ["1 2 +"] |> should equal expected [] let ``Addition - errors if there is nothing on the stack`` () = let expected = None evaluate ["+"] |> should equal expected [] let ``Addition - errors if there is only one value on the stack`` () = let expected = None evaluate ["1 +"] |> should equal expected [] let ``Addition - more than two values on the stack`` () = let expected = Some [1; 5] evaluate ["1 2 3 +"] |> should equal expected [] let ``Subtraction - can subtract two numbers`` () = let expected = Some [-1] evaluate ["3 4 -"] |> should equal expected [] let ``Subtraction - errors if there is nothing on the stack`` () = let expected = None evaluate ["-"] |> should equal expected [] let ``Subtraction - errors if there is only one value on the stack`` () = let expected = None evaluate ["1 -"] |> should equal expected [] let ``Subtraction - more than two values on the stack`` () = let expected = Some [1; 9] evaluate ["1 12 3 -"] |> should equal expected [] let ``Multiplication - can multiply two numbers`` () = let expected = Some [8] evaluate ["2 4 *"] |> should equal expected [] let ``Multiplication - errors if there is nothing on the stack`` () = let expected = None evaluate ["*"] |> should equal expected [] let ``Multiplication - errors if there is only one value on the stack`` () = let expected = None evaluate ["1 *"] |> should equal expected [] let ``Multiplication - more than two values on the stack`` () = let expected = Some [1; 6] evaluate ["1 2 3 *"] |> should equal expected [] let ``Division - can divide two numbers`` () = let expected = Some [4] evaluate ["12 3 /"] |> should equal expected [] let ``Division - performs integer division`` () = let expected = Some [2] evaluate ["8 3 /"] |> should equal expected [] let ``Division - errors if dividing by zero`` () = let expected = None evaluate ["4 0 /"] |> should equal expected [] let ``Division - errors if there is nothing on the stack`` () = let expected = None evaluate ["/"] |> should equal expected [] let ``Division - errors if there is only one value on the stack`` () = let expected = None evaluate ["1 /"] |> should equal expected [] let ``Division - more than two values on the stack`` () = let expected = Some [1; 4] evaluate ["1 12 3 /"] |> should equal expected [] let ``Combined arithmetic - addition and subtraction`` () = let expected = Some [-1] evaluate ["1 2 + 4 -"] |> should equal expected [] let ``Combined arithmetic - multiplication and division`` () = let expected = Some [2] evaluate ["2 4 * 3 /"] |> should equal expected [] let ``Combined arithmetic - multiplication and addition`` () = let expected = Some [13] evaluate ["1 3 4 * +"] |> should equal expected [] let ``Combined arithmetic - addition and multiplication`` () = let expected = Some [7] evaluate ["1 3 4 + *"] |> should equal expected [] let ``Dup - copies a value on the stack`` () = let expected = Some [1; 1] evaluate ["1 dup"] |> should equal expected [] let ``Dup - copies the top value on the stack`` () = let expected = Some [1; 2; 2] evaluate ["1 2 dup"] |> should equal expected [] let ``Dup - errors if there is nothing on the stack`` () = let expected = None evaluate ["dup"] |> should equal expected [] let ``Drop - removes the top value on the stack if it is the only one`` () = let expected: int list option = Some [] evaluate ["1 drop"] |> should equal expected [] let ``Drop - removes the top value on the stack if it is not the only one`` () = let expected = Some [1] evaluate ["1 2 drop"] |> should equal expected [] let ``Drop - errors if there is nothing on the stack`` () = let expected = None evaluate ["drop"] |> should equal expected [] let ``Swap - swaps the top two values on the stack if they are the only ones`` () = let expected = Some [2; 1] evaluate ["1 2 swap"] |> should equal expected [] let ``Swap - swaps the top two values on the stack if they are not the only ones`` () = let expected = Some [1; 3; 2] evaluate ["1 2 3 swap"] |> should equal expected [] let ``Swap - errors if there is nothing on the stack`` () = let expected = None evaluate ["swap"] |> should equal expected [] let ``Swap - errors if there is only one value on the stack`` () = let expected = None evaluate ["1 swap"] |> should equal expected [] let ``Over - copies the second element if there are only two`` () = let expected = Some [1; 2; 1] evaluate ["1 2 over"] |> should equal expected [] let ``Over - copies the second element if there are more than two`` () = let expected = Some [1; 2; 3; 2] evaluate ["1 2 3 over"] |> should equal expected [] let ``Over - errors if there is nothing on the stack`` () = let expected = None evaluate ["over"] |> should equal expected [] let ``Over - errors if there is only one value on the stack`` () = let expected = None evaluate ["1 over"] |> should equal expected [] let ``User-defined words - can consist of built-in words`` () = let expected = Some [1; 1; 1] evaluate [": dup-twice dup dup ;"; "1 dup-twice"] |> should equal expected [] let ``User-defined words - execute in the right order`` () = let expected = Some [1; 2; 3] evaluate [": countup 1 2 3 ;"; "countup"] |> should equal expected [] let ``User-defined words - can override other user-defined words`` () = let expected = Some [1; 1; 1] evaluate [": foo dup ;"; ": foo dup dup ;"; "1 foo"] |> should equal expected [] let ``User-defined words - can override built-in words`` () = let expected = Some [1; 1] evaluate [": swap dup ;"; "1 swap"] |> should equal expected [] let ``User-defined words - can override built-in operators`` () = let expected = Some [12] evaluate [": + * ;"; "3 4 +"] |> should equal expected [] let ``User-defined words - can use different words with the same name`` () = let expected = Some [5; 6] evaluate [": foo 5 ;"; ": bar foo ;"; ": foo 6 ;"; "bar foo"] |> should equal expected [] let ``User-defined words - can define word that uses word with the same name`` () = let expected = Some [11] evaluate [": foo 10 ;"; ": foo foo 1 + ;"; "foo"] |> should equal expected [] let ``User-defined words - cannot redefine non-negative numbers`` () = let expected = None evaluate [": 1 2 ;"] |> should equal expected [] let ``User-defined words - cannot redefine negative numbers`` () = let expected = None evaluate [": -1 2 ;"] |> should equal expected [] let ``User-defined words - errors if executing a non-existent word`` () = let expected = None evaluate ["foo"] |> should equal expected [] let ``User-defined words - only defines locally`` () = evaluate [": + - ;"; "1 1 +"] |> should equal (Some [0]) evaluate ["1 1 +"] |> should equal (Some [2]) [] let ``Case-insensitivity - DUP is case-insensitive`` () = let expected = Some [1; 1; 1; 1] evaluate ["1 DUP Dup dup"] |> should equal expected [] let ``Case-insensitivity - DROP is case-insensitive`` () = let expected = Some [1] evaluate ["1 2 3 4 DROP Drop drop"] |> should equal expected [] let ``Case-insensitivity - SWAP is case-insensitive`` () = let expected = Some [2; 3; 4; 1] evaluate ["1 2 SWAP 3 Swap 4 swap"] |> should equal expected [] let ``Case-insensitivity - OVER is case-insensitive`` () = let expected = Some [1; 2; 1; 2; 1] evaluate ["1 2 OVER Over over"] |> should equal expected [] let ``Case-insensitivity - user-defined words are case-insensitive`` () = let expected = Some [1; 1; 1; 1] evaluate [": foo dup ;"; "1 FOO Foo foo"] |> should equal expected [] let ``Case-insensitivity - definitions are case-insensitive`` () = let expected = Some [1; 1; 1; 1] evaluate [": SWAP DUP Dup dup ;"; "1 swap"] |> should equal expected