问题
Let's say that I want to print something simple like this table:
January 1
February 2
March 3
April 4
May 5
June 6
July 7
August 8
September 9
October 10
November 11
December 12
I'd like to accomplish this like:
for(tm i{ 0, 0, 0, 1, 0 }; i.tm_mon < 12; ++i.tm_mon) cout << put_time(&i, "%-9B") << i.tm_mon + 1 << endl;
Unfortunately puttime
doesn't seem to allow me to use field flags in it's format fields. Additionally this puttime
doesn't seem to play nice with setw
.
Is my only option to do strftime
and then use that with setw
?
回答1:
Here is a header-only library that respects the I/O manipulators:
#include "date.h"
#include <iomanip>
#include <iostream>
int
main()
{
using namespace date;
using namespace std;
auto m = jan;
do
{
cout << left << setw(10) << format("%B", sys_days{m/1/1}) << right
<< unsigned(m) << '\n';
} while (++m != jan);
}
You can try this out yourself by pasting the above code into this wandbox link.
January 1
February 2
March 3
April 4
May 5
June 6
July 7
August 8
September 9
October 10
November 11
December 12
回答2:
The following will also work
for(tm i{ 0, 0, 0, 1, 0 }; i.tm_mon < 12; ++i.tm_mon)
{
std::stringstream oss;
oss << std::put_time(&i, "%B");
string str = oss.str();
cout << std::setiosflags(std::ios::left) << setw( 10 ) << str << setw( 2 ) << i.tm_mon + 1 << endl;
}
来源:https://stackoverflow.com/questions/40132424/how-can-i-format-width-in-puttime