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format.cc
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format.cc
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/** @example format.cc
*
* An example of using the string formatting system, including various
* differences from C such as user defined type and range formatting.
*/
#include <unordered_map>
#include <vector>
#include <tuple>
#include <clocale>
#include <ostd/algorithm.hh>
#include <ostd/range.hh>
#include <ostd/io.hh>
using namespace ostd;
using namespace ostd::string_literals;
struct Foo {
};
/* implementing formatting for custom objects */
template<>
struct ostd::format_traits<Foo> {
template<typename R>
static void to_format(Foo const &, R &writer, format_spec const &fs) {
switch (fs.spec()) {
case 'i':
range_put_all(writer, "Foo_i"_sr);
break;
default:
range_put_all(writer, "Foo_s"_sr);
break;
}
if (fs.flags() & FMT_FLAG_AT) {
range_put_all(writer, "_esc"_sr);
}
}
};
int main() {
std::vector<int> x = { 5, 10, 15, 20 };
/* prints [5|10|15|20] (using | as the delimiter and %s for each item),
* the syntax for ranges is %(CONTENTS%) where CONTENTS is a sequence
* up until and including the last format mark followed by a delimiter,
* so for example "%s, " has "%s" for formatting and ", " for the delimiter
* and "%d: %s, " has "%d: %s" for format and ", " for the delimiter; if
* you need to specify a complicated manual delimiter, you can use the
* "FORMAT%|DELIMITER" syntax, where %(%s, %) equals %(%s%|, %)
*/
writeln("-- range format --");
writefln("[%(%s|%)]", x);
/* prints a range with default format {item, item, item, ...}
* you can enable item escaping by passing the @ flag
*/
writeln("\n-- range default format --");
writefln("%s", x);
int y[] = { 2, 4, 8, 16, 32 };
/* prints { 2, 4, 8, 16, 32 } using ", " as the delimiter */
writeln("\n-- range format of static array --");
writefln("{ %(%s, %) }", y);
/* nested range printing - prints each item of the main
* range with [ %(%s, %) ] and ",\n" as the delimiter
*/
writeln("\n-- range format of nested range --");
writefln("[\n%([ %(%s, %) ]%|,\n%)\n]", map(range(10), [](int v) {
return range(v + 1);
}));
std::unordered_map<std::string, int> m = {
{ "foo", 5 },
{ "bar", 10 },
{ "baz", 15 }
};
/* prints something like { "baz": 15, "bar": 10, "foo": 5 }, note that
* the tuple is expanded into two formats (using the # flag) and the
* items are escaped with the @ flag (applies to strings and chars)
*/
writeln("\n-- range format of hash table --");
writefln("{ %#(%@s: %d, %) }", m);
/* not escaped, you get { baz: 15, bar: 10, foo: 5} */
writeln("\n-- range format of hash table (no escape) --");
writefln("{ %#(%s: %d, %) }", m);
/* no expansion of the items, print entire tuple with default format,
* gets you something like { <"baz", 15>, <"bar", 10>, <"foo", 5> }
* because the default tuple format is <item, item, item, ...>
*/
writeln("\n-- range format of hash table (no item expansion) --");
writefln("{ %(%@s, %) }", m);
/* as the @ flag enables escaping on strings and chars,
* you can use it standalone outside of range/tuple format
*/
writeln("\n-- format item escaping --");
writefln("not escaped: %s, escaped: %@s", "foo", "bar");
std::tuple<std::string, int, float, std::string> tup{
"hello world", 1337, 3.14f, "test"
};
/* you can expand tuples similarly to ranges, with %<CONTENTS%> where
* CONTENTS is a regular format string like if the tuple was formatted
* separately with each item of the tuple passed as a separate argument
*/
writeln("\n-- tuple format --");
writefln("the tuple contains %<%@s, %d, %f, %s%>.", tup);
writeln("\n-- tuple default format --");
writefln("auto tuple: %s", tup);
writeln("\n-- tuple default format (escaped) --");
writefln("auto tuple with escape: %@s", tup);
std::tuple<int, float, char const *> xt[] = {
std::make_tuple(5, 3.14f, "foo"),
std::make_tuple(3, 1.23f, "bar"),
std::make_tuple(9, 8.66f, "baz")
};
/* formatting a range of tuples, with each tuple expanded using #
*/
writeln("\n-- range of tuples format --");
writefln("[ %#(<%d|%f|%@s>%|, %) ]", xt);
/* formatting custom objects, the information about the format mark
* is passed into the to_format function and the object can read it
*/
writeln("\n-- custom object format --");
writefln("%s", Foo{});
writefln("%i", Foo{});
writefln("%@s", Foo{});
writefln("%@i", Foo{});
auto s = appender<std::string>();
/* formatting into a string sink (can be any output range, but
* appender makes sure the capacity is unlimited so it's safe)
*/
writeln("\n-- format into a string --");
format(s, "hello %s", "world");
writeln(s.get());
/* locale specific formatting */
writeln("\n-- number format with C locale --");
writefln(
"\"%d\", \"%f\", \"%X\"", 123456789, 12345.6789123, 0x123456789ABCDEF
);
cout.imbue(std::locale{""});
writefln("\n-- number format with system locale --");
writefln(
"\"%d\", \"%f\", \"%X\"", 123456789, 12345.6789123, 0x123456789ABCDEF
);
}
/* output:
-- range format --
[5|10|15|20]
-- range default format --
{5, 10, 15, 20}
-- range format of static array --
{ 2, 4, 8, 16, 32 }
-- range format of nested range --
[
[ 0 ],
[ 0, 1 ],
[ 0, 1, 2 ],
[ 0, 1, 2, 3 ],
[ 0, 1, 2, 3, 4 ],
[ 0, 1, 2, 3, 4, 5 ],
[ 0, 1, 2, 3, 4, 5, 6 ],
[ 0, 1, 2, 3, 4, 5, 6, 7 ],
[ 0, 1, 2, 3, 4, 5, 6, 7, 8 ],
[ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]
]
-- range format of hash table --
{ "baz": 15, "bar": 10, "foo": 5 }
-- range format of hash table (no escape) --
{ baz: 15, bar: 10, foo: 5 }
-- range format of hash table (no item expansion) --
{ <"baz", 15>, <"bar", 10>, <"foo", 5> }
-- format item escaping --
not escaped: foo, escaped: "bar"
-- tuple format --
the tuple contains "hello world", 1337, 3.140000, test.
-- tuple default format --
auto tuple: <hello world, 1337, 3.14, test>
-- tuple default format (escaped) --
auto tuple with escape: <"hello world", 1337, 3.14, "test">
-- range of tuples format --
[ <5|3.140000|"foo">, <3|1.230000|"bar">, <9|8.660000|"baz"> ]
-- custom object format --
Foo_s
Foo_i
Foo_s_esc
Foo_i_esc
-- format into a string --
hello world
-- number format with C locale --
"123456789", "12345.678912", "123456789ABCDEF"
-- number format with system locale --
"123 456 789", "12 345,678912", "123 456 789 ABC DEF"
*/