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Give parse more useful output, add more useful errors

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osmarks 2017-08-17 15:30:43 +01:00
parent 372160b040
commit 52b3b5f889
1 changed files with 7 additions and 3 deletions
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10
src/Expr.elm
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@ -16,7 +16,8 @@ type Expr
num : Parser () Expr num : Parser () Expr
num = num =
Num <$> Num.float <|> Num << toFloat <$> Num.int (Num <$> Num.float <|> Num << toFloat <$> Num.int)
<?> "expected a number (int or float)"
stringIs : String -> a -> Parser s a stringIs : String -> a -> Parser s a
stringIs str val = stringIs str val =
@ -33,12 +34,15 @@ op =
group : Parser () Expr group : Parser () Expr
group = group =
between (string "(") (string ")") (sepBy1 whitespace (lazy <| \_ -> parser)) -- Avoid bad recursion issues using lazy parser evaluation between (string "(") (string ")") (sepBy1 whitespace (lazy <| \_ -> parser)) -- Avoid bad recursion issues using lazy parser evaluation
<?> "expected a group (whitespace-separated expressions between brackets)"
|> map Group |> map Group
parser : Parser () Expr parser : Parser () Expr
parser = parser =
(lazy <| \_ -> group) <|> op <|> num (lazy <| \_ -> group) <|> op <|> num
parse : String -> Result (ParseErr ()) (ParseOk () Expr) parse : String -> Result (List String) Expr
parse = parse =
Combine.parse parser Combine.parse parser
>> Result.mapError (\(_, _, errorList) -> errorList)
>> Result.map (\(_, _, expr) -> expr) -- Convert errors/results to nicer format