A new formatting library that tries to be simple to understand while still being powerful and providing more convenience features than other libraries (like functions for pretty-printing maps and lists, or a function for printing arbitrary datatypes using generics).
A comparison with other libraries:
Text.Printf) takes a formatting string and uses some type tricks to accept the rest of the arguments polyvariadically. It's very concise, but there are some drawbacks – it can't produce
Text(you'd have to
T.packit every time) and it doesn't warn you at compile-time if you pass wrong arguments or not enough of them.
text-format takes a formatting string with curly braces denoting places where arguments would be substituted (the arguments themselves are provided via a tuple). If you want to apply formatting to some of the arguments, you have to use one of the provided formatters. Like
printf, it can fail at runtime, but at least the formatters are first-class (and you can add new ones).
formatting takes a formatting template consisting of pieces of strings interleaved with formatters; this ensures that arguments always match their placeholders.
formattingprovides lots of formatters and generally seems to be the most popular formatting library here. Unfortunately, at least in my experience writing new formatters can be awkward and people sometimes have troubles understanding how
fmt (i.e. this library) provides formatters that are ordinary functions, and a bunch of operators for concatenating formatted strings; those operators also do automatic conversion. There are some convenience formatters which aren't present in
formatting(like ones for formatting maps, lists, converting to base64, etc). Some find the operator syntax annoying, while others like it.
HasCallStackto partial functions.
instance FromBuilder ByteString(for both lazy and strict bytestrings) and
instance FromBuilder BS.Builder. These instances generate UTF8-encoded bytestrings. This allows producing formatting strings for various HTTP libraries that are intent on using
pretty :: (Buildable a, FromBuilder b) => a -> bfor formatting anything as
Buildable. There’s also
prettyLnfor consistency with
double-conversiondependency (which was sometimes causing compilation issues). As the result,
floatFhave become slower.
precFformatter was removed completely because its semantics was too confusing. You can use
Numeric.showGFloatto achieve a similar effect.
floatFnow always prints a point, even if the number is integral.
tupleLikeFhas been removed.
TupleFnow has an additional instance that lets
tupleFbe used to format lists.
base16-bytestringdependency was removed.
Compatibility with GHC 7.6 and 7.8 was dropped.
From this version on,
blockListFnever puts blank lines between items. If you want blank lines between items, I’m afraid that you’ll have to add them manually (by e.g. adding a blank line to each item).
blockListF'can be used to create lists with custom bullets.
|+because HLint can’t handle
#|and everyone uses HLint apparently.
- Added time formatters (see
formatLnto be polyvariadic.
genericFfor formatting arbitrary data.
|#because they turn out to be easier to type.
Added a migration guide from
Changed output of
text-format, because in some cases it’s nicer than brackets.
indent'to always add newlines.
Added some formatters:
- formatters for lists, maps and tuples (
baseFand floating-point formatters
hexFwhich works on both numbers and bytestrings
- padding and trimming formatters
- conditionals (
Fmtbecause orphan instances are controversial.
Exported internal classes and functions from
Made all operators associate to the right (
Builderdocumentation says it’s faster than the opposite).
>%%<so that it’d be possible to write
%<a>%%<b>%instead of weird
%<< ... >>%, which work work
Buildable. If you don’t care about speed and just want to output something, use them.
IO ()instance in
Fmt.IO. If you import that module, raw formatted strings would print themselves.
Changed fixities of operators so that
Changed license to BSD3 since all our dependencies are BSD3 and we can’t use MIT.
First (completely experimental) release.