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I can add integers!

This commit is contained in:
sforman 2023-07-29 06:54:15 -07:00
parent 5315edbe83
commit 48f6e78196
1 changed files with 52 additions and 1 deletions
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53
implementations/Elm/src/Joy.elm
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@ -14,6 +14,54 @@ type alias JoyList = List JoyType
joy : (List JoyType) -> (List JoyType) -> Result String (List JoyType)
joy stack expression =
case expression of
[] ->
Ok stack
term :: rest_of_expression ->
case term of
JoySymbol symbol ->
case joy_eval symbol stack rest_of_expression of
Err msg -> Err msg
Ok (s, e) -> joy s e
_ ->
joy (term :: stack) rest_of_expression
joy_eval : String -> (List JoyType) -> (List JoyType) -> Result String (List JoyType, List JoyType)
joy_eval symbol stack expression =
case symbol of
"+" -> joy_add stack expression
_ -> Err ("Unknown word: " ++ symbol)
joy_add : (List JoyType) -> (List JoyType) -> Result String (List JoyType, List JoyType)
joy_add stack expression =
case pop_int(stack) of
Err msg -> Err msg
Ok (a, s0) ->
case pop_int(s0) of
Err msg -> Err msg
Ok (b, s1) ->
let c = a + b in
Ok ((push_int c s1), expression)
push_int : Int -> (List JoyType) -> (List JoyType)
push_int i stack = (JoyInt i) :: stack
pop_int : (List JoyType) -> Result String (Int, List JoyType)
pop_int stack =
case stack of
[] -> Err "Not enough values on Stack"
h :: t ->
case h of
JoyInt i ->
Ok (i, t)
_ ->
Err "Not an integer."
-- Printer
@ -114,5 +162,8 @@ text_to_expression text = parse (tokenize text)
doit text =
case text_to_expression text of
Err msg -> Err msg
Ok ast -> Ok (joyExpressionToString ast)
Ok ast ->
case joy [] ast of
Err msg -> Err msg
Ok expr -> Ok (joyExpressionToString expr)