Tips, tricks and hacks by @jfischoff
- Tweets 469
- Following 4
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Haskell Tips retweeted
So apparently a lot of peeps still don't know you can avoid pressing 'up' a billion times going through :reload's in GHCi by adding this to your `~/.haskeline` file:
historyDuplicates: IgnoreAll
Have fun.
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Haskell Tips retweeted
Open this page: hackage.haskell.org/package/…
... and then type 's' to open a quick search for any exported symbols in lens
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Usually one starts with the first error and works forward. With the default setting one has to scroll up over and over again.
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Use `ghci -freverse-errors` or `stack repl --ghc-options=-freverse-errors` to reverse the error order; see the first error with no scrolling
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() does not add a “null” value to every type, hell no; () is a “dull” value in a type of its own: () - @pigworker
personal.cis.strath.ac.uk/co…
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Avoid lengthy computation in a exception handler with `catch`. The exception handler has async exceptions masked: hackage.haskell.org/package/…
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Careful with your foralls
data A = forall a. A {x :: a} -- existential quantification
data A = A {x :: forall a. a} -- polymorphic component
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Use the '+RTS -qg' flag to speed up your programs.
/ht @stdlib
inner-haven.net/posts/2017-0…
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IORef can't unbox primitives, but URef, Ptr and others can and are thus faster: medium.com/@jonathangfischof…
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class ToB a where
to∷a → B
class FromB a where
from∷Parser a
-- vs
class Bable a where
to∷a → B
from∷Parser a
medium.com/@jonathangfischof…
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(Pattern Matching : Data Constructors :: Type Class Instance Selection : Type Constructors) / ordering
medium.com/@jonathangfischof…
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If you are using `putStr` you probably want to
> import System.IO
> hSetBuffering stdout NoBuffering
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Data.List.\\ doesn't remove duplicates:
> import Data.List
> [1, 1, 2] \\ [1, 2]
[1]
For set difference use Data.Set.\\
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If you want to run a function from the command line:
> echo 'foo "hello"' | ghci src/File.hs
If you want to run `main`:
> runhaskell Main.hs
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To list all @Hackage packages
> cabal list
With just the word "lens"
> cabal list lens
For a summary of the package 'lens'
> cabal info lens
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