@@ -1,76 +1,227 @@
1−# Using `streamly` package
1+<!--
2+Portions (c) 2020, Google LLC.
3+SPDX-License-Identifer: BSD-3-Clause
3−If you are new to Haskell please take a look at [Haskell Getting Started
6+# Getting started with the `streamly` package
4−Guide](https://github.com/composewell/haskell-dev/blob/master/getting-started.rst).
6−The following instructions assume that you are using a shell on a POSIX
8+This guide will show you how to write a simple program that uses
7−system. On Windows you need a shell under `msys`, some of the commands
9+`streamly`, using the [`cabal`](https://www.haskell.org/cabal/) build
8−may have slight differences.
10+manager for Haskell.
10−## Which version to use?
12+<!-- TODO: Add instructions for `stack` and `nix`.
12−* [Latest stable release](https://hackage.haskell.org/package/streamly) is available on
14+If you are using `stack` or `nix` please make sure to add the latest
13− Hackage.
15+version from Hackage to your tool configuration. -->
14−* [Latest development version](https://github.com/composewell/streamly) is
17−If you are using `stack` or `nix` please make sure to add the latest version
17+No prior knowledge of either Haskell or of `cabal` is needed. We do
18−from Hackage to your tool configuration.
18+however assume that you are using a command-line shell on a POSIX
19+operating system. If you are running Windows™ then you may need
20+to run a command-line shell under `msys` and some of the commands
21+below may also need to be changed in small ways to make them work.
20−## Recommended build options
23+**Note**: If you are new to Haskell you may find the [Haskell Getting
25+Guide](https://github.com/composewell/haskell-dev/blob/master/getting-started.rst)
22−See [recommended compilation options here](docs/Build.md).
28+If you know your way around Haskell, and have an up to date toolchain
29+already installed, then you can jump straight to the section titled
30+"[_Prepare Your Build Directory_](#user-content-prepare-your-build-directory)".
24−## Using with `cabal`
32+## Getting started with `streamly` using `cabal`
26−Make sure you have `cabal` version 3.0 or later installed and you have `ghc`
34+To get started, you will need a recent `cabal` binary to be installed
27−available in your PATH. Refresh your package list:
35+on your system.
37+### Installing `cabal`
39+A pre-packaged `cabal` binary may already be available for your
42+For example, on Debian GNU/Linux, you could install `cabal` using::
45+$ sudo apt install cabal-install
50+You would also need to install the Glasgow Haskell Compiler `ghc`. In
51+most operating systems, using the system's package manager to install
52+`cabal` would also bring in a version of `ghc` as a dependency.
54+Please verify that `ghc` is present:
58+The Glorious Glasgow Haskell Compilation System, version 8.0.2
61+If `ghc` isn't present, please install it using your operating
62+system's package manager. For example, on Debian GNU/Linux, use:
65+$ sudo apt install ghc
68+### Update `cabal` if necessary
70+Many operating systems ship an old version of `cabal`; in order to use
71+`streamly` you should use `cabal` version 3.0 (or later).
73+You can check the installed version of `cabal` by using its
79+$ /usr/bin/cabal --version
80+cabal-install version 1.24.0.2
81+compiled using version 1.24.2.0 of the Cabal library
84+In this example, the installed `cabal` binary is too old for our
85+needs. It would need to be upgraded.
87+You can ask `cabal` to upgrade itself (please see
88+<https://www.haskell.org/cabal/>):
91+$ cabal install Cabal cabal-install
92+Resolving dependencies...
93+Downloading base16-bytestring-0.1.1.7...
94+... lots of build output ...
95+Building cabal-install-3.0.0.0...
96+Installed cabal-install-3.0.0.0
99+`cabal` will usually place its compiled binaries inside the directory
102+You can verify the version of your newly installed binary by using the
103+`--version` flag again:
106+$ $HOME/.cabal/bin/cabal --version
107+cabal-install version 3.0.0.0
108+compiled using version 3.0.2.0 of the Cabal library
111+If you have upgraded `cabal`, do be sure to specify `$HOME/.cabal/bin`
112+early in your `PATH` shell variable, so that the new binary gets used
113+instead of the older version on your system.
116+$ PATH=$HOME/.cabal/bin:$PATH
119+Once you have `cabal` version 3.0 (or later) successfully installed,
120+please refresh its package list by using `cabal update`.
30$ cabal update
123$ cabal update
124+Downloading the latest package list from hackage.haskell.org
127+### Prepare Your Build Directory
33−Create a directory for isolated builds:
129+Next, create a build directory, so that you can use `cabal`'s isolated
36$ mkdir streamly-play
133$ mkdir streamly-play
39−Create a `.cabal` file:
137+Run `cabal init` to create an initial set of project files:
43$ cabal init --minimal --dependency base --dependency streamly
140$ cabal init --minimal --dependency base --dependency streamly
142+Generating LICENSE...
143+... other messages ...
144+Generating Main.hs...
145+Generating streamly-play.cabal...
147+Warning: no synopsis given. You should edit the .cabal file and add one.
148+You may want to edit the .cabal file and add a Description field.
46−You can add any other dependencies as well later on by editing the
151+This invocation will set up a build with two build dependencies,
152+namely `base` and `streamly`. You can add additional dependencies
47−`build-depends` section of the cabal file.
153+later, by editing the `build-depends` section of the generated cabal
154+file `streamly-play.cabal`. Please see the [Cabal User
155+Guide](https://www.haskell.org/cabal/users-guide/) for more
156+information on how to configure `cabal`.
49−### Using hackage version in repl
158+This invocation also creates a skeletal `Main.hs` program which we
51−Run repl with the latest version from Hackage:
161+### Try `streamly` in the GHCi REPL
163+You can now try out `streamly` using the `GHCi` interpreter's
164+read-eval-print-loop (REPL) facility.
166+To start up the GHCi REPL using the released `streamly` version on
54$ cabal repl --build-depends streamly
170$ cabal repl --build-depends streamly
171+... plenty of build messaages, the first time around ...
55GHCi, version 8.8.3: https://www.haskell.org/ghc/ :? for help
172GHCi, version 8.8.3: https://www.haskell.org/ghc/ :? for help
56[1 of 1] Compiling Main ( Main.hs, interpreted )
173[1 of 1] Compiling Main ( Main.hs, interpreted )
57Ok, one module loaded.
174Ok, one module loaded.
178+Once at the `*Main>` prompt, you can import `streamly` and use it
182+*Main> import qualified Streamly.Prelude as S
58−*Main> S.drain $ S.mapM print $ S.fromList [1..3]
184+*Main S> S.drain $ S.mapM print $ S.fromList [1..3]
65−Run repl with a specific version from Hackage:
191+For the curious, here is a high level overview of what these lines
194+1. `import qualified Streamly.Prelude as S` imports the Streamly
195+ prelude into GHCi, and makes it available as module `S`.
196+2. `[1..3]` generates the Haskell list `[1, 2, 3]`.
197+3. `S.fromList` transforms that list into a stream of integers.
198+4. `S.mapM print` transforms the stream of integers into a stream of
199+ actions that would print those integers when executed.
200+5. `S.drain` transforms that stream of actions into an IO action that
201+ `main` or GHCi's REPL can execute.
203+These concepts are explained in greater detail in the [Streamly
206+#### Using a specific version of `streamly` in the REPL
208+You can also ask `cabal` to use a specific version of `streamly` by
209+adding a version number constraint to the `--build-depends` flag:
68$ cabal repl --build-depends streamly==0.7.2
212$ cabal repl --build-depends streamly==0.7.2
213+[1 of 1] Compiling Main ( Main.hs, interpreted )
214+Ok, modules loaded: Main.
71−### Using github version in repl
218+#### (Advanced) Using the development version of `streamly` in the REPL
220+To use the development version of `streamly`, we need to configure
221+`cabal` to fetch it from Github.
73−Create a `cabal.project` file with the following contents:
223+Create a `cabal.project` file in the current directory with the
76packages: .
227packages: .
@@ -80,17 +231,26 @@ source-repository-package
80 tag: master
231 tag: master
83−Run repl:
234+With this file present, `cabal` will fetch and build the current
235+version of `streamly` from Github every time it is run. For example:
86$ cabal repl
238$ cabal repl
239+... fetches the 'master' branch of streamly from Github ...
240+... build messages ...
241+[1 of 1] Compiling Main v ( Main.hs, interpreted )
242+Ok, modules loaded: Main.
89−### Hello World!
246+### Using `streamly` in a standalone program
91−Edit `Main.hs` as follows:
248+Let us now turn the single-line stanza above into a standalone program
249+that uses `streamly`.
93−```
251+Edit `Main.hs` to contain the following:
94module Main where
254module Main where
96import qualified Streamly.Prelude as S
256import qualified Streamly.Prelude as S
@@ -99,8 +259,40 @@ main :: IO ()
99main = S.drain $ S.mapM print $ S.fromList [1..3]
259main = S.drain $ S.mapM print $ S.fromList [1..3]
102−Build and run:
262+Build and run this program using `cabal run`:
105$ cabal run
265$ cabal run
266+... build messages ...
272+## Which version of `streamly` should you use?
274+If you are new to Streamly, we recommend using latest [stable release
275+of streamly][streamly-hackage] on Hackage.
277+If you need access to cutting edge features (and do not mind the
278+occasional breakage), please use the [development version of
279+streamly][streamly-github] on Github.
284+If you got this far successfully, congratulations!
286+* For an overview of the `streamly` package, please read the
287+ [Streamly Tutorial][tutorial].
288+* Please browse the code examples in the
289+ [`examples`](./examples/README.md) directory.
290+* If you would like to start on a real world project, please take a
291+ look at the [recommended compilation options](./docs/Build.md).
294+<!-- Markdown Links -->
296+ [tutorial]: https://hackage.haskell.org/package/streamly/docs/Streamly-Tutorial.html
297+ [streamly-hackage]: https://hackage.haskell.org/package/streamly
298+ [streamly-github]: https://github.com/composewell/streamly