# elm/parser
> Regular expressions are quite confusing and difficult to use. This library provides a coherent alternative that handles more cases and produces clearer code.
>
> (Readme.md from the [package](https://package.elm-lang.org/packages/elm/parser/latest/))
```
type alias Point =
{ x : Float
, y : Float
}
point : Parser Point
point =
succeed Point
|. symbol "("
|. spaces
|= float
|. spaces
|. symbol ","
|. spaces
|= float
|. spaces
|. symbol ")"
```
This is a summary of the talk [Demystifying Parsers](https://www.youtube.com/watch?v=M9ulswr1z0E) by Tereza Sokol.
## Basics
| Function | Description |
| --------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------- |
| [run](https://package.elm-lang.org/packages/elm/parser/latest/Parser#run) : Parser a -> String -> Result (List DeadEnd) a | Runs the Parser on a String |
| [int](https://package.elm-lang.org/packages/elm/parser/latest/Parser#int) : Parser Int | Parser for Int |
| [float](https://package.elm-lang.org/packages/elm/parser/latest/Parser#float) : Parser Float | Parser for Float |
| [oneOf](https://package.elm-lang.org/packages/elm/parser/latest/Parser#oneOf) : List (Parser a) -> Parser a | Trys different Parsers. Uses the first that succeeds.
Once the parser matches the first element, there is no going back!
|
| [andThen](https://package.elm-lang.org/packages/elm/parser/latest/Parser#andThen) : (a -> Parser b) -> Parser a -> Parser b | Applys the first parser and if successful applies the second. Fails if one of the parsers fails. |
## Pipeline
{% hint style="info" %}
This subject is explained at [4:48 in the Video](https://youtu.be/M9ulswr1z0E?t=288).
{% endhint %}
| Function | Description |
| ----------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [succeed](https://package.elm-lang.org/packages/elm/parser/latest/Parser#succeed) : a -> Parser a | Starts the Pipeline. a -> Parser a is the constructor.
For a record Point use the structur called Point .
|
| [(\|=)](https://package.elm-lang.org/packages/elm/parser/latest/Parser#\(\|=\)) : Parser (a -> b) -> Parser a -> Parser b | Keeps an element. |
| [(\|.)](https://package.elm-lang.org/packages/elm/parser/latest/Parser#\(\|.\)) : Parser keep -> Parser ignore -> Parser keep | Eats a character and throws it away. |
| [spaces](https://package.elm-lang.org/packages/elm/parser/latest/Parser#spaces) : Parser () | Represents whitespace |
## Strings
{% hint style="info" %}
This subject is explained at [7:20 in the Video](https://youtu.be/M9ulswr1z0E?t=440).
{% endhint %}
| Function | Description |
| ------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------- |
| [chompWhile](https://package.elm-lang.org/packages/elm/parser/latest/Parser#chompWhile) : (Char -> Bool) -> Parser () | Looks for zero or more characters that succeeds the check. Stops as soon as the check fails. |
| [chompIf](https://package.elm-lang.org/packages/elm/parser/latest/Parser#chompIf) : (Char -> Bool) -> Parser () | Reads one symbols. |
| [getChompedString](https://package.elm-lang.org/packages/elm/parser/latest/Parser#getChompedString) : Parser a -> Parser String | Returnes the string that got chomped |
## Loops
{% hint style="info" %}
This subject is explained at [14:10 in the Video](https://youtu.be/M9ulswr1z0E?t=440).
{% endhint %}
| Function | Description |
| ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------- |
| [loop](https://package.elm-lang.org/packages/elm/parser/latest/Parser#loop) : state -> (state -> Parser ([Step](https://package.elm-lang.org/packages/elm/parser/latest/Parser#Step) state a)) -> Parser a | Takes an initial state and a parser step and returns a parser. |
| type [Step](https://package.elm-lang.org/packages/elm/parser/latest/Parser#Step) state a = Loop state \| Done a | A parser step just specifies if it should continue looping or stop. |
## Error messages
{% hint style="info" %}
This subject is explained at [17:04 in the Video](https://youtu.be/M9ulswr1z0E?t=1024).
{% endhint %}
| Function | Description |
| ------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------ |
| [problem](https://package.elm-lang.org/packages/elm/parser/latest/Parser#problem) : String -> Parser a | Returns the error message and ends the parsing. The argument is the actuall message. |
## Further Reading
* 🎥**Video:** [Demystifying Parsers](https://www.youtube.com/watch?v=M9ulswr1z0E) by Tereza Sokol
* 📄**Thread:** [Elm parser question](https://www.reddit.com/r/elm/comments/bcb2fi/elm_parser_question/)
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