Haskell parsec operator try issue

Question

I am compiling on Windows using GHC. Here is my code for reference http://hpaste.org/86539 The problem is that the following expression does not parse: `3+2 < 1+-4 <= -3 << 1`. It should parse as: .. however, I get unexpected `-` when it is clearly the highest operator. I suspect it's because of my usage of `try` on line 55, however without it `<` and `<<` and operators that are repetitions of one symbol do not parse correctly. I am seeking advice or hints.

Accepted Answer

The problem is on line 56:

```
P.lexeme <$ string s
```

Should read:

```
P.lexeme gmlLexer $ string s
```

The former construct was matching `s`, then returning the function `P.lexeme` as the result of the parse! The subsequent `>>` threw the result away, hence it type checked.

What you wanted to do was the later line: Apply the `P.lexeme` for your language `gmlLexer` to the parser for matching `s`.

Haskell parsec operator try issue

Solution

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