Understanding on what lit and src behaviors

[Rizary]

@natefaubion, continuing my chat in slack, and trying to avoid slack archive.. i'll put my reply in here.

Here is the guide said:

```  -- | `lit x` will match exactly the path component `x`.
  -- | For example, `lit "x"` matches `/x`.
  lit :: String -> f Unit

  -- | `str` matches any path string component.
  -- | For example, `str` matches `/foo` as `"foo"`.
  str :: f String```

I just want to correct my logic in how purescript-routing act. So, my understanding is, the library trying to match the uri address with the pattern we describe in routing :: Match a function. How it works is it stripped the uri address (let say mysite.com/#/foo/bar/FooBar) until the # sign.

So, we will have #/foo/bar/FooBar, which in this case, if we use the above guide, lit "x" matches "/x" and "str" matches "/foo" as "foo", then the stripped address can be matched with this:

#/foo        /bar         /FooBar
  (lit "foo") (lit "bar") (lit "FooBar")

but instead, i have to do this:

#/foo                     /bar                    /FooBar
  (lit "" <* lit "foo") (lit "" <*lit "bar") (lit "" <* lit "FooBar")

and if we see the guide again, it looks like it is "//foo//bar//FooBar". I know that we use <* or *> that supposed to remove the lit "". But why can't we just use the former example one??? I mean why we can't just write it :
FooBarPage <$ (lit "foo" *> lit "bar" *> lit "FooBar" )

Instead of:

FooBarPage <$ (lit "" *> lit "foo" *> lit "" *> lit "bar" *> lit "" *> lit "FooBar" )

the same goes if we have FooBarPage String, by using the guide again, we supposed to write:

FooBarPage <$> (lit "foo" *> lit "bar" *> lit "" *> lit "FooBar" )

instead of
FooBarPage <$ (lit "" *> lit "foo" *> lit "" *> lit "bar" *> lit "FooBar" )

Right? I am sorry if my understanding is not what the guide supposed to mean. But from beginner pov (like me), reading the source's comment explanation is very helpful (well i have to try and error by building it though for better understanding).

Anyway, this is just me trying to visualise what the lib do.

[natefaubion]

The parser matches on slugs in between slashes (or rather, it's tokenized using slashes as delimiters). lit "bar" matches bar literally, not /bar. So given foo/bar/baz, the parser matches on tokens [ "foo", "bar", "baz" ]. Given /foo/bar/baz, the parser matches on tokens [ "", "foo", "bar", "baz" ], which is why you need lit "" to match the root slash.

[Rizary]

i see.. so we need the lit "" only at the first time, not every / that we have..

And also it means, we cannot parse if there isn't any / in the address. For an example i want to parse like the following url:

https://matrix.hackage.haskell.org/#/package/a50#GHC-7.6/a50-0.2

as there is not / in between the a50 and GHC-70, the a50#GHC-7.6 will be tokenized as one string? How can we dealing with this case?

[natefaubion]

I think that https://matrix.hackage.haskell.org/#/package/a50#GHC-7.6/a50-0.2 would likely be tokenized as [ "", "package", "a50#GHC-7.6", "a50-0.2" ]. The parser does not recursively tokenize on #, it just drops everything until the first #.

[Rizary]

@natefaubion noted and thank you..