From 6ca0662862dffcc67ff4016aaa04cf314d81608e Mon Sep 17 00:00:00 2001
From: defanor <defanor@uberspace.net>
Date: Sat, 16 Dec 2017 06:11:12 +0300
Subject: Generate usage strings for help messages

---
 README.md | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

(limited to 'README.md')

diff --git a/README.md b/README.md
index bcefff4..cb38e87 100644
--- a/README.md
+++ b/README.md
@@ -8,8 +8,8 @@ while keeping them language-agnostic and more user- and shell
 scripting-friendly than JSON and similar formats.
 
 Given a type, it derives instances to print and parse it as
-command-line arguments. The resulting deserialization wouldn't be as
-nice as that of
+command-line arguments, as well as to compose usage instructions. The
+resulting deserialization wouldn't be as nice as that of
 e.g.
 [optparse-generic](https://hackage.haskell.org/package/optparse-generic),
 but the aim here is to handle more or less arbitrary types.
@@ -46,6 +46,12 @@ What would look like this in a shell:
 --foobar foo 1 'a string' bar
 ```
 
+And its usage string -- like this:
+
+```
+[--something STRING] [--foobar (foo INT STRING | bar)] (foo INT STRING | bar)
+```
+
 More verbose versions can be produced and parsed with
 `alwaysUseSelName = True` and/or `omitNamedOptions = False`:
 
@@ -54,3 +60,33 @@ More verbose versions can be produced and parsed with
 nothing just foo 1 'a string' bar
 --something nothing --foobar just foo --arg1 1 --arg2 'a string' --foobar2 bar
 ```
+
+And here is output of the `help` function from the same file, with all
+the (alwaysUseSelName, omitNamedOptions) combinations:
+
+```
+(True,True)
+["--foo","[]","--bar","a string"]
+--foo ([] | : INT ([] | :...)) [--bar STRING]
+(True,True)
+["--foo","[]"]
+--foo ([] | : INT ([] | :...)) [--bar STRING]
+(True,False)
+["--foo","[]","--bar","just","a string"]
+--foo ([] | : INT ([] | :...)) --bar (nothing | just STRING)
+(True,False)
+["--foo","[]","--bar","nothing"]
+--foo ([] | : INT ([] | :...)) --bar (nothing | just STRING)
+(False,True)
+["[]","--bar","a string"]
+([] | : INT ([] | :...)) [--bar STRING]
+(False,True)
+["[]"]
+([] | : INT ([] | :...)) [--bar STRING]
+(False,False)
+["[]","just","a string"]
+([] | : INT ([] | :...)) (nothing | just STRING)
+(False,False)
+["[]","nothing"]
+([] | : INT ([] | :...)) (nothing | just STRING)
+```
-- 
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