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@ -63,7 +63,7 @@ features some combinators that are missing in other parsing libraries:
* `observing` allows to “observe” parse errors without ending parsing (they
are returned in `Left`, while normal results are wrapped in `Right`).
In addition to that, Megaparsec 6 features high-performance combinators
In addition to that, Megaparsec features high-performance combinators
similar to those found in Attoparsec:
* `tokens` makes it easy to parse several tokens in a row (`string` and
@ -76,9 +76,8 @@ similar to those found in Attoparsec:
* `takeP` allows to grab n tokens from the stream and returns them as a
“chunk” of the stream.
So now that we have matched the main “performance boosters” of Attoparsec,
Megaparsec 6 is not significantly slower than Attoparsec if you write your
parser carefully (see also [the section about performance](#performance)).
Megaparsec is about as fast as Attoparsec if you write your parser carefully
(see also [the section about performance](#performance)).
Megaparsec can currently work with the following types of input stream
out-of-the-box:
@ -92,12 +91,9 @@ users have done so many times.
### Error messages
Megaparsec 5 introduced well-typed error messages and the ability to use
custom data types to adjust the library to specific domain of interest. No
need to use a shapeless bunch of strings.
The design of parse errors has been revised in version 6 significantly, but
custom errors are still easy (probably even easier now).
Megaparsec has well-typed error messages and the ability to use custom data
types to adjust the library to specific domain of interest. No need to use a
shapeless bunch of strings.
Megaparsec 7 introduced the `ParseErrorBundle` data type that helps to
manage multi-error messages and pretty-print them easily and efficiently.
@ -108,8 +104,8 @@ line the default.
Megaparsec works well with streams of tokens produced by tools like Alex.
The design of the `Stream` type class has been changed significantly in
version 6, but user can still work with custom streams of tokens without
problems.
versions 6 and 7, but user can still work with custom streams of tokens
without problems.
### Character and binary parsing
@ -158,18 +154,18 @@ to migrate to Megaparsec.
## Performance
Despite being flexible, Megaparsec is also quite fast. Here is how
Megaparsec 6.4.0 compares to Attoparsec 0.13.2.0 (the fastest widely used
parsing library in the Haskell ecosystem):
Despite being flexible, Megaparsec is also fast. Here is how Megaparsec
7.0.0 compares to Attoparsec 0.13.2.2 (the fastest widely used parsing
library in the Haskell ecosystem):
Test case | Execution time | Allocated | Max residency
------------------|---------------:|----------:|-------------:
CSV (Attoparsec) | 57.14 μs | 397,912 | 10,560
CSV (Megaparsec) | 76.27 μs | 557,272 | 9,120
Log (Attoparsec) | 244.2 μs | 1,181,120 | 11,144
Log (Megaparsec) | 315.2 μs | 1,485,776 | 11,392
JSON (Attoparsec) | 14.39 μs | 132,496 | 9,048
JSON (Megaparsec) | 26.70 μs | 233,336 | 9,424
CSV (Attoparsec) | 76.50 μs | 397,784 | 10,544
CSV (Megaparsec) | 64.69 μs | 352,408 | 9,104
Log (Attoparsec) | 302.8 μs | 1,150,032 | 10,912
Log (Megaparsec) | 337.8 μs | 1,246,496 | 10,912
JSON (Attoparsec) | 18.20 μs | 128,368 | 9,032
JSON (Megaparsec) | 25.45 μs | 203,824 | 9,176
The benchmarks were created to guide development of Megaparsec 6 and can be
found [here](https://github.com/mrkkrp/parsers-bench).
@ -189,9 +185,9 @@ let's compare Megaparsec with some of them.
library for parsing. Although the both libraries deal with parsing, it's
usually easy to decide which you will need in particular project:
* *Attoparsec* is faster but not that feature-rich. It should be used when
you want to process large amounts of data where performance matters more
than quality of error messages.
* *Attoparsec* is sometimes faster but not that feature-rich. It should be
used when you want to process large amounts of data where performance
matters more than quality of error messages.
* *Megaparsec* is good for parsing of source code or other human-readable
texts. It has better error messages and it's implemented as monad
@ -344,6 +340,7 @@ The following are some prominent projects that use Megaparsec:
Here are some blog posts mainly announcing new features of the project and
describing what sort of things are now possible:
* [Megaparsec 7](https://markkarpov.com/post/megaparsec-7.html)
* [Evolution of error messages](https://markkarpov.com/post/evolution-of-error-messages.html)
* [A major upgrade to Megaparsec: more speed, more power](https://markkarpov.com/post/megaparsec-more-speed-more-power.html)
* [Latest additions to Megaparsec](https://markkarpov.com/post/latest-additions-to-megaparsec.html)