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Error type (not just a string.) 

This is mostly for fun, but I bet it comes in handy, eh?

At the very least, it's a nice catalog of the possible errors that the
basic Joy system might encounter.
This commit is contained in:
sforman 2023-07-30 14:59:09 -07:00
parent 850bc3a500
commit 1089ab7c24
1 changed files with 101 additions and 41 deletions
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142
implementations/Elm/src/Joy.elm
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@ -22,14 +22,72 @@ type alias JoyDict =
Dict String JList Dict String JList
type JoyErr
= UnknownWord
| EmptyDefinition
| DefinitionNameMustBeSymbol
| CannotTakeFirstOfEmptyList
| CannotTakeRestOfEmptyList
| CannotBoolify
| NotEnoughValuesOnStack
| NotAnInteger
| NotAList
| NotABooleanValue
| MissingClosingBracket
| ExtraClosingBracket
-- Joy functions take a stack and expression and return a stack and -- Joy functions take a stack and expression and return a stack and
-- expression, but something might go wrong, so they really return a -- expression, but something might go wrong, so they really return a
-- Result value. -- Result value.
type alias JoyFunction = JList -> JList -> Result String ( JList, JList )
type alias JoyFunction =
JList -> JList -> Result JoyErr ( JList, JList )
joy : JList -> JList -> JoyDict -> Result String ( JList, JoyDict ) joy_err : JoyErr -> String
joy_err err =
case err of
UnknownWord ->
"Unknown word."
EmptyDefinition ->
"Empty definition."
DefinitionNameMustBeSymbol ->
"Def name isn't symbol."
CannotTakeFirstOfEmptyList ->
"Cannot take first of empty list."
CannotTakeRestOfEmptyList ->
"Cannot take rest of empty list."
CannotBoolify ->
"Cannot Boolify."
NotEnoughValuesOnStack ->
"Not enough values on Stack"
NotAnInteger ->
"Not an integer."
NotAList ->
"Not a list."
NotABooleanValue ->
"Not a Boolean value."
MissingClosingBracket ->
"Missing closing bracket."
ExtraClosingBracket ->
"Extra closing bracket."
joy : JList -> JList -> JoyDict -> Result JoyErr ( JList, JoyDict )
joy stack expression dict = joy stack expression dict =
case expression of case expression of
[] -> [] ->
@ -49,7 +107,7 @@ joy stack expression dict =
joy (term :: stack) rest_of_expression dict joy (term :: stack) rest_of_expression dict
joy_eval : String -> JList -> JList -> JoyDict -> Result String ( JList, JList, JoyDict ) joy_eval : String -> JList -> JList -> JoyDict -> Result JoyErr ( JList, JList, JoyDict )
joy_eval symbol stack expression dict = joy_eval symbol stack expression dict =
if symbol == "" then if symbol == "" then
Ok ( stack, expression, dict ) Ok ( stack, expression, dict )
@ -59,18 +117,20 @@ joy_eval symbol stack expression dict =
else else
case joy_function_eval symbol stack expression of case joy_function_eval symbol stack expression of
Err msg -> Err err ->
if "Unknown word." == msg then case err of
-- Look up word in dictionary. UnknownWord ->
case get symbol dict of -- Look up word in dictionary.
Just definition -> case get symbol dict of
Ok ( stack, definition ++ expression, dict ) Just definition ->
Ok ( stack, definition ++ expression, dict )
Nothing -> Nothing ->
Err ("Unknown word: " ++ symbol) Err UnknownWord
else -- ("Unknown word: " ++ symbol)
Err msg _ ->
Err err
Ok ( stack0, expression0 ) -> Ok ( stack0, expression0 ) ->
Ok ( stack0, expression0, dict ) Ok ( stack0, expression0, dict )
@ -208,16 +268,16 @@ joy_function_eval symbol stack expression =
joy_truthy stack expression joy_truthy stack expression
_ -> _ ->
Err "Unknown word." Err UnknownWord
joy_inscribe : JList -> JList -> JoyDict -> Result String ( JList, JList, JoyDict ) joy_inscribe : JList -> JList -> JoyDict -> Result JoyErr ( JList, JList, JoyDict )
joy_inscribe stack expression dict = joy_inscribe stack expression dict =
case pop_list stack of case pop_list stack of
Ok ( def, s0 ) -> Ok ( def, s0 ) ->
case def of case def of
[] -> [] ->
Err "Empty definition." Err EmptyDefinition
sym :: body -> sym :: body ->
-- check that name is a symbol -- check that name is a symbol
@ -226,7 +286,7 @@ joy_inscribe stack expression dict =
Ok ( s0, expression, insert name body dict ) Ok ( s0, expression, insert name body dict )
_ -> _ ->
Err "Def name isn't symbol." Err DefinitionNameMustBeSymbol
Err msg -> Err msg ->
Err msg Err msg
@ -399,7 +459,7 @@ joy_first stack expression =
Ok ( push_any b s0, expression ) Ok ( push_any b s0, expression )
Err _ -> Err _ ->
Err "Cannot take first of empty list." Err CannotTakeFirstOfEmptyList
Err msg -> Err msg ->
Err msg Err msg
@ -424,7 +484,7 @@ joy_rest stack expression =
Ok ( push_list el s0, expression ) Ok ( push_list el s0, expression )
Err _ -> Err _ ->
Err "Cannot take rest of empty list." Err CannotTakeRestOfEmptyList
Err msg -> Err msg ->
Err msg Err msg
@ -486,7 +546,7 @@ joy_truthy stack expression =
Ok ( JoyTrue :: s0, expression ) Ok ( JoyTrue :: s0, expression )
JoySymbol _ -> JoySymbol _ ->
Err "Cannot Boolify." Err CannotBoolify
Err msg -> Err msg ->
Err msg Err msg
@ -516,52 +576,52 @@ push_any j stack =
j :: stack j :: stack
pop_int : JList -> Result String ( Int, JList ) pop_int : JList -> Result JoyErr ( Int, JList )
pop_int stack = pop_int stack =
pop_any stack |> andThen isnt_int pop_any stack |> andThen isnt_int
pop_list : JList -> Result String ( JList, JList ) pop_list : JList -> Result JoyErr ( JList, JList )
pop_list stack = pop_list stack =
pop_any stack |> andThen isnt_list pop_any stack |> andThen isnt_list
pop_bool : JList -> Result String ( Bool, JList ) pop_bool : JList -> Result JoyErr ( Bool, JList )
pop_bool stack = pop_bool stack =
pop_any stack |> andThen isnt_bool pop_any stack |> andThen isnt_bool
pop_any : JList -> Result String ( JoyType, JList ) pop_any : JList -> Result JoyErr ( JoyType, JList )
pop_any stack = pop_any stack =
case stack of case stack of
[] -> [] ->
Err "Not enough values on Stack" Err NotEnoughValuesOnStack
item :: rest -> item :: rest ->
Ok ( item, rest ) Ok ( item, rest )
isnt_int : ( JoyType, JList ) -> Result String ( Int, JList ) isnt_int : ( JoyType, JList ) -> Result JoyErr ( Int, JList )
isnt_int ( item, stack ) = isnt_int ( item, stack ) =
case item of case item of
JoyInt i -> JoyInt i ->
Ok ( i, stack ) Ok ( i, stack )
_ -> _ ->
Err "Not an integer." Err NotAnInteger
isnt_list : ( JoyType, JList ) -> Result String ( JList, JList ) isnt_list : ( JoyType, JList ) -> Result JoyErr ( JList, JList )
isnt_list ( item, stack ) = isnt_list ( item, stack ) =
case item of case item of
JoyList el -> JoyList el ->
Ok ( el, stack ) Ok ( el, stack )
_ -> _ ->
Err "Not a list." Err NotAList
isnt_bool : ( JoyType, JList ) -> Result String ( Bool, JList ) isnt_bool : ( JoyType, JList ) -> Result JoyErr ( Bool, JList )
isnt_bool ( item, stack ) = isnt_bool ( item, stack ) =
case item of case item of
JoyTrue -> JoyTrue ->
@ -571,7 +631,7 @@ isnt_bool ( item, stack ) =
Ok ( False, stack ) Ok ( False, stack )
_ -> _ ->
Err "Not a Boolean value." Err NotABooleanValue
@ -633,17 +693,17 @@ tokenator tok =
-- instead turning them into symbols! -- instead turning them into symbols!
expect_right_bracket : List String -> JList -> Result String ( JList, List String ) expect_right_bracket : List String -> JList -> Result JoyErr ( JList, List String )
expect_right_bracket tokens acc = expect_right_bracket tokens acc =
case tokens of case tokens of
[] -> [] ->
Err "Missing closing bracket." Err MissingClosingBracket
h :: t -> h :: t ->
expect_right_bracket_one_token_lookahead h t acc expect_right_bracket_one_token_lookahead h t acc
expect_right_bracket_one_token_lookahead : String -> List String -> JList -> Result String ( JList, List String ) expect_right_bracket_one_token_lookahead : String -> List String -> JList -> Result JoyErr ( JList, List String )
expect_right_bracket_one_token_lookahead token tokens acc = expect_right_bracket_one_token_lookahead token tokens acc =
case token of case token of
"]" -> "]" ->
@ -677,11 +737,11 @@ expect_right_bracket_one_token_lookahead token tokens acc =
---(* token -> token list -> joy_type * token list *) ---(* token -> token list -> joy_type * token list *)
one_token_lookahead : String -> List String -> Result String ( JoyType, List String ) one_token_lookahead : String -> List String -> Result JoyErr ( JoyType, List String )
one_token_lookahead token tokens = one_token_lookahead token tokens =
case token of case token of
"]" -> "]" ->
Err "Extra closing bracket." Err ExtraClosingBracket
"[" -> "[" ->
case expect_right_bracket tokens [] of case expect_right_bracket tokens [] of
@ -695,7 +755,7 @@ one_token_lookahead token tokens =
Ok ( tokenator token, tokens ) Ok ( tokenator token, tokens )
parse0 : List String -> JList -> Result String JList parse0 : List String -> JList -> Result JoyErr JList
parse0 tokens acc = parse0 tokens acc =
case tokens of case tokens of
[] -> [] ->
@ -731,11 +791,11 @@ doit text dict =
Ok ( expr, dict0 ) -> Ok ( expr, dict0 ) ->
Ok ( joyExpressionToString expr, dict0 ) Ok ( joyExpressionToString expr, dict0 )
Err msg -> Err err ->
Err msg Err (joy_err err)
Err msg -> Err err ->
Err msg Err (joy_err err)
add_def : String -> JoyDict -> JoyDict add_def : String -> JoyDict -> JoyDict