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