parsec | Protocol for Asynchronous , Reliable , Secure and Efficient

What you want is a parser which skip any unmatched chars, then parse a regex pattern followed.

The date pattern could be defined with regex parser,

Did you define the bin size for your histogram and also the x axis. You should define the x axis to be the same for both histograms and give them the same number of bins in each histogram. Then when you plot them they should be identcle along the x axis but different bin heights for the different bins.

You can define this with (<$) :: Functor f => a -> f b -> f a. This thus performs a functor mapping with x <$ u = fmap (const x) u:

It seems that one of your symbols does not come from where you expect. However, it is difficult to tell exactly where the problem is, as you give just a part of your compiled code instead of something self-contained.

https://stackoverflow.com/help/minimal-reproducible-example

As mentioned in the comment by Silvio Mayolo, the compiler seems unable to see that "\r\n" is a String object, hence a list of Chars, hence an instance of the Foldable class.

The error message does not say that the header was included multiple times. It says that the same symbol exists in multiple object files and the header file is just the source of that symbol.

If an H file defines a symbol, then in fact every C file that includes it will define that symbol because only a compiled file can define a symbol and H files are not compiled, they are included into C files when those C files are compiled (actually when they are preprocessed but that usually happens when they are compiled). And if multiple C files define the same symbol, are compiled, and linked together (note that this is a ld error, so it is a linker error), you end up with multiple symbols of the same name, which is not allowed by C standard.

If a H file just wants to inform a C file about the existence and type of a symbol that is defined elsewhere, e.g. in another C file, it must only declare the symbol by prefixing it with extern.

You don't need a permutation parser. Simple old many is fine. You can use Either to temporarily make them the same type, then partitionEithers to split them back out.

This change was made March 2, 2009 in commit a98a3ccb by Antoine Latter. The commit comment was just:

The problem with typeAssignment1 is that "is" and "a" are perfectly valid parameter parses. So, the parameter parsing gobbles up the whole input until nothing is left, and then you get an error. In fact, if you look closely at that error you see this to be true: the parser is expecting either a space (for more parameters) or "is a" (the terminal of your whole parser).

On the other hand, typeAssignment2 is really close, but it seems that you're not handling spaces properly. In order to parse many parameters, you need to parse all the spaces between those parameter, not just the first one.

I think the following alternative should do the trick:

If, in your problem domain, failure should never modify the state, the most straightforward thing to do is to invert the layers: