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Gabriel Gonzalez 2015-09-02 11:02:54 -07:00
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@ -1,19 +1,16 @@
% Haskell for Shell Scripting
% Gabriel Gonzalez
% April 8, 2015
% September 3, 2015
# Before class
If you haven't installed `ghc`, yet:
If you haven't installed `ghc`, visit:
```bash
$ echo "/home/ggonzalez/tools/ghc-7.8.3-Darwin.x86_64" >> ~/.tools
$ sync-dottools.sh
```
* [https://www.haskell.org/downloads](https://www.haskell.org/downloads)
... then open a new terminal window.
... and install a GHC distribution appropriate to your operating system.
To test your Haskell installation, run these commands:
To test your Haskell installation, run these commands from a terminal:
```bash
$ echo 'main = putStrLn "Hello, world!"' > hello.hs
@ -25,7 +22,7 @@ Install the shell scripting library using these commands:
```bash
$ cabal update
$ cabal install turtle-1.1.0
$ cabal install turtle-1.2.1
```
# Outline
@ -253,6 +250,8 @@ The top level of a Haskell program is declarative and only allows definitions
You cannot execute code at the top level
The runtime only executes `main`!
# Subroutines
Use `do` to create a subroutine that runs more than one command:
@ -950,15 +949,15 @@ Prelude Turtle> format "I take 0 arguments"
```haskell
(%) :: Format b c -> Format a b -> Format a c
"A " :: Format a a
s :: Format a (String -> a)
" string that takes " :: Format a a
d :: Format a (Int -> a)
" arguments" :: Format a a
"A " :: Format a a
s :: Format a (Text -> a)
" string that takes " :: Format a a
d :: Format a (Int -> a)
" arguments" :: Format a a
"A "%s%" string that takes "%d%" arguments" :: Format a (Text -> Int -> a)
format "A "%s%" string that takes "%d%" arguments" :: Text -> Int -> Text
format ("A "%s%" string that takes "%d%" arguments") :: Text -> Int -> Text
```
You can build your own format specifiers!
@ -1498,7 +1497,7 @@ Fold.head :: Fold a (Maybe a)
```
```haskell
ls :: Shell Turtle.FilePath
ls "/tmp" :: Shell Turtle.FilePath
fold :: Shell a -> Fold a b -> IO b
fold (ls "/tmp") :: Fold Turtle.FilePath b -> IO b
@ -1733,13 +1732,5 @@ tuple = do
You can use Haskell as a "better Bash", getting types for free without slow
startup times or heavyweight syntax.
If you want others to run your Haskell scripts, they can use `dottools` to install
`ghc` on their machine.
I also have a relocatable `ghc` uploaded to Packer that you can use to interpret
scripts on Mesos.
We also have an internal Hackage server at Twitter (go/hackage)
Visit https://hackage.haskell.org/package/turtle for more extensive documentation
on the shell scripting library we used today