fmt
A new formatting library
Version on this page: | 0.5.0.0@rev:1 |
LTS Haskell 23.19: | 0.6.3.0 |
Stackage Nightly 2025-04-30: | 0.6.3.0 |
Latest on Hackage: | 0.6.3.0 |
fmt-0.5.0.0@sha256:83de9575d840e0dc10cf39461331ce105b06e6939a144faa0f53968d0b81afed,4767
Module documentation for 0.5.0.0
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:
printf
(fromText.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 produceText
(you'd have toT.pack
it 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 angle brackets 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.
formatting
provides 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 howformatting
works.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.
Changes
0.5.0.0
-
From this version on,
blockListF
never 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). -
Now
blockListF'
can be used to create lists with custom bullets. -
Added
unwordsF
andunlinesF
. -
Added the
F
suffix toindent
andindent'
.
0.4.0.0
- Renamed
#|
and|#
to+|
and|+
because HLint can’t handle#|
and everyone uses HLint apparently.
0.3.0.0
- Added time formatters (see
Fmt.Time
).
0.2.0.0
- Changed
format
andformatLn
to be polyvariadic.
0.1.0.0
-
Added
genericF
for formatting arbitrary data. -
Changed
%<
and>%
to#|
and|#
because they turn out to be easier to type. -
Added a migration guide from
formatting
. -
Changed output of
eitherF
. -
Added bechmarks.
0.0.0.4
-
Added
format
fromtext-format
, because in some cases it’s nicer than brackets. -
Renamed
padCenterF
topadBothF
. -
Modified
indent
andindent'
to always add newlines.
0.0.0.3
-
Wrote documentation.
-
Added some formatters:
indent
- formatters for lists, maps and tuples (
listF
, etc) octF
,binF
,baseF
and floating-point formattershexF
which works on both numbers and bytestringsordinalF
andcommaizeF
- padding and trimming formatters
base64F
andbase64UrlF
- conditionals (
whenF
andunlessF
)
-
Merged
Fmt.IO
withFmt
because orphan instances are controversial. -
Exported internal classes and functions from
Fmt.Internal
. -
Added
fmt
andfmtLn
. -
Made all operators associate to the right (
Builder
documentation says it’s faster than the opposite). -
Reexported
Buildable
andBuilder
.
0.0.0.2
-
Added
>%%<
so that it’d be possible to write%<a>%%<b>%
instead of weird%<a%<b>%
. -
Added
%<< ... >>%
, which work workShow
instead ofBuildable
. If you don’t care about speed and just want to output something, use them. -
Added an
IO ()
instance inFmt.IO
. If you import that module, raw formatted strings would print themselves. -
Added tests.
-
Changed fixities of operators so that
%<n+1>%
would work. -
Changed license to BSD3 since all our dependencies are BSD3 and we can’t use MIT.
0.0.0.1
First (completely experimental) release.