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+# args
+A simple, small, flexible, single-header C++11 argument parsing library
+
+This is designed to somewhat replicate the behavior of Python's argparse, but
+in C++, with static type checking, and hopefully a lot faster.
+
+UTF-8 support is limited at best.  No normalization is performed, so non-ascii
+characters are very best kept out of flags, and combined glyphs are probably
+going to mess up help output if you use it.
+
+This program is MIT-licensed, so you can use the header as-is with no
+restrictions. I'd appreciate attribution in a README, Man page, or something if
+you are feeling generous, but all that's required is that you don't remove the
+license and my name from the header of the args.hxx file in source
+redistributions (ie. don't pretend that you wrote it).  I do welcome additions
+and updates wherever you feel like contributing code.
+
+There is no API documentation here.  The APIs that are most important are the
+ArgumentParser and the constructors of the individual types.  The examples
+should be, for the most part, enough to use this library, but the API
+documentation will come soon enough.
+
+# What does it do
+
+It:
+
+* lets you handle flags, flag+arguments, and positional arguments simply and
+	elegently, with the full help of static typechecking.
+* allows you to use your own types in a pretty simple way.
+* lets you use count flags, and lists of all argument-accepting types.
+* Allows full validation of groups of required arguments, though output isn't
+	pretty when something fails group validation.  User validation functions are
+	accepted.  Groups are fully nestable.
+* Generates pretty help for you, with some good tweakable parameters.
+* Lets you customize all prefixes and most separators, allowing you to create
+	an infinite number of different argument syntaxes
+* Lets you parse, by default, any type that has a stream extractor operator for
+	it.  If this doesn't work, you can supply a function and parse the string
+	yourself if you like.
+
+# What does it not do
+
+There are tons of things this library does not do!
+
+It does not yet:
+
+* Allow you to use a positional argument list before any other positional
+	arguments (the last argument list will slurp all subsequent positional
+	arguments).  The logic for allowing this would be a lot more code than I'd
+	like, and would make static checking much more difficult, requiring us to
+	sort std::string arguments and pair them to positional arguments before
+	assigning them, rather than what we currently do, which is assiging them as
+	we go for better simplicity and speed.
+
+It will not ever:
+
+* Allow you to create subparsers like argparse
+* Allow one argument flag to take a specific number of arguments
+	(like `--foo first second`).  You can instead split that with a flag list
+	(`--foo first --foo second`) or a custom type extraction
+	(`--foo first,second`)
+* Allow you to intermix multiple different prefix types (eg. `++foo` and
+	`--foo` in the same parser), though shortopt and longopt prefixes can be
+	different.
+
+# Examples
+
+All the code examples here will be complete code examples, with some output.
+
+## Simple example:
+
+```c++
+	args::ArgumentParser parser("This is a test program.", "This goes after the options.");
+	args::HelpFlag help(parser, "help", "Display this help menu", args::Matcher({'h'}, {"help"}));
+	try
+	{
+		parser.ParseCLI(argc, argv);
+	}
+	catch (args::Help)
+	{
+		std::cout << parser.Help();
+		return 0;
+	}
+	catch (args::ParseError e)
+	{
+		std::cerr << e.what() << std::endl;
+		std::cerr << parser.Help();
+		return 1;
+	}
+	return 0;
+}
+```
+
+```shell
+ % ./test
+ % ./test -h
+  ./test {OPTIONS} 
+
+    This is a test program. 
+
+  OPTIONS:
+
+      -h, --help         Display this help menu 
+
+    This goes after the options. 
+ % 
+```
+
+## Boolean flags, special group types, different matcher construction:
+
+```c++
+#include <iostream>
+
+#include <args.hxx>
+
+int main(int argc, char **argv)
+{
+	args::ArgumentParser parser("This is a test program.", "This goes after the options.");
+	args::Group group(parser, "This group is all exclusive", args::Group::Validators::Xor);
+	args::Flag foo(group, "foo", "The foo flag", args::Matcher({'f'}, {"foo"}));
+	args::Flag bar(group, "bar", "The bar flag", args::Matcher({'b'}));
+	args::Flag baz(group, "baz", "The baz flag", args::Matcher({"baz"}));
+	try
+	{
+		parser.ParseCLI(argc, argv);
+	}
+	catch (args::Help)
+	{
+		std::cout << parser.Help();
+		return 0;
+	}
+	catch (args::ParseError e)
+	{
+		std::cerr << e.what() << std::endl;
+		std::cerr << parser.Help();
+		return 1;
+	}
+	catch (args::ValidationError e)
+	{
+		std::cerr << e.what() << std::endl;
+		std::cerr << parser.Help();
+		return 1;
+	}
+	if (foo) { std::cout << "foo" << std::endl; }
+	if (bar) { std::cout << "bar" << std::endl; }
+	if (baz) { std::cout << "baz" << std::endl; }
+	return 0;
+}
+```
+
+```shell
+ % ./test   
+Group validation failed somewhere!
+  ./test {OPTIONS} 
+
+    This is a test program. 
+
+  OPTIONS:
+
+      -f, --foo          The foo flag 
+      -b                 The bar flag 
+      --baz              The baz flag 
+
+    This goes after the options. 
+ % ./test -f
+foo
+ % ./test --foo
+foo
+ % ./test --foo -f
+foo
+ % ./test -b      
+bar
+ % ./test --baz
+baz
+ % ./test --baz -f
+Group validation failed somewhere!
+  ./test {OPTIONS} 
+
+    This is a test program. 
+...
+ % ./test --baz -fb
+Group validation failed somewhere!
+  ./test {OPTIONS} 
+...
+ % 
+```
+
+## Argument flags, Positional arguments, lists
+
+```c++
+```
+
+```shell
+% ./test -h
+  ./test {OPTIONS} [foo] [numbers...] 
+
+    This is a test program. 
+
+  OPTIONS:
+
+      -h, --help         Display this help menu 
+      -i integer         The integer flag 
+      -c characters      The character flag 
+      foo                The foo position 
+      numbers            The numbers position list 
+      "--" can be used to terminate flag options and force all following
+      arguments to be treated as positional options 
+
+    This goes after the options. 
+ % ./test -i 5
+i: 5
+ % ./test -i 5.2
+Argument 'integer' received invalid value type '5.2'
+  ./test {OPTIONS} [foo] [numbers...] 
+ % ./test -c 1 -c 2 -c 3
+c: 1
+c: 2
+c: 3
+ % 
+ % ./test 1 2 3 4 5 6 7 8 9
+f: 1
+n: 2
+n: 3
+n: 4
+n: 5
+n: 6
+n: 7
+n: 8
+n: 9
+ % ./test 1 2 3 4 5 6 7 8 9 a
+Argument 'numbers' received invalid value type 'a'
+  ./test {OPTIONS} [foo] [numbers...] 
+
+    This is a test program. 
+...
+```
+
+# Custom type parsers (here we use std::tuple)
+
+```c++
+#include <iostream>
+#include <tuple>
+
+#include <args.hxx>
+
+std::istream& operator>>(std::istream& is, std::tuple<int, int>& ints)
+{
+    is >> std::get<0>(ints);
+    is.get();
+    is >> std::get<1>(ints);
+    return is;
+}
+
+void DoublesReader(const std::string &name, const std::string &value, std::tuple<double, double> &destination)
+{
+    size_t commapos = 0;
+    std::get<0>(destination) = std::stod(value, &commapos);
+    std::get<1>(destination) = std::stod(std::string(value, commapos + 1));
+}
+
+int main(int argc, char **argv)
+{
+    args::ArgumentParser parser("This is a test program.");
+    args::PosArg<std::tuple<int, int>> ints(parser, "INTS", "This takes a pair of integers.");
+    args::PosArg<std::tuple<double, double>, DoublesReader> doubles(parser, "DOUBLES", "This takes a pair of doubles.");
+    try
+    {
+        parser.ParseCLI(argc, argv);
+    }
+    catch (args::Help)
+    {
+        std::cout << parser.Help();
+        return 0;
+    }
+    catch (args::ParseError e)
+    {
+        std::cerr << e.what() << std::endl;
+        std::cerr << parser.Help();
+        return 1;
+    }
+    if (ints)
+    {
+        std::cout << "ints found: " << std::get<0>(ints.value) << " and " << std::get<1>(ints.value) << std::endl;
+    }
+    if (doubles)
+    {
+        std::cout << "doubles found: " << std::get<0>(doubles.value) << " and " << std::get<1>(doubles.value) << std::endl;
+    }
+    return 0;
+}
+```
+
+```shell
+ % ./test -h
+Argument could not be matched: 'h'
+  ./test [INTS] [DOUBLES] 
+
+    This is a test program. 
+
+  OPTIONS:
+
+      INTS               This takes a pair of integers. 
+      DOUBLES            This takes a pair of doubles. 
+
+ % ./test 5
+ints found: 5 and 0
+ % ./test 5,8
+ints found: 5 and 8
+ % ./test 5,8 2.4,8
+ints found: 5 and 8
+doubles found: 2.4 and 8
+ % ./test 5,8 2.4, 
+terminate called after throwing an instance of 'std::invalid_argument'
+  what():  stod
+zsh: abort      ./test 5,8 2.4,
+ % ./test 5,8 2.4 
+terminate called after throwing an instance of 'std::out_of_range'
+  what():  basic_string::basic_string: __pos (which is 4) > this->size() (which is 3)
+zsh: abort      ./test 5,8 2.4
+ % ./test 5,8 2.4-7
+ints found: 5 and 8
+doubles found: 2.4 and 7
+ % ./test 5,8 2.4,-7
+ints found: 5 and 8
+doubles found: 2.4 and -7
+```
+
+As you can see, with your own types, validation can get a little weird.  Make
+sure to check and throw a parsing error (or whatever error you want to catch)
+if you can't fully deduce your type.  The built-in validator will only throw if
+there are unextracted characters left in the stream.