Center numbers in a cell

[whitenite1]

I decided I wanted to write a simple spreadsheet program. Just adding, subtracting, etc., in specified cells. Each cell is 13 characters wide. I would like to be able to center a number or decimal entered, or the result of the math done on the the desired cells.

void Print_Spreadsheet (vector<vector<Cell>>& Spreadsheet, int column, int row)
{
	int a, b, wide = 11, high=18, len, num;
	double fl;
	string rub(13,' ');//Remove contents of entered cell
	for( a=1;a<wide;a++)
	{
		gotoXY(7+(14*a), 1, Spreadsheet[0][a+column].text + " ");
		for( b=1;b<high;b++)
		{
			gotoXY(6, 1+(b*2));
			if(Spreadsheet[b+row][0].number < 10)
				cout << " ";
			cout << Spreadsheet[b+row][0].number;
			gotoXY(1+(14*a), 1+(b*2),rub);

			if(Spreadsheet[b+row][a+column].number != -1)
			{
				len=6;// Start. Centers the results
				num = Spreadsheet[b+row][a+column].number;
				if(num>99)
					len-=1;
				if(num>999)
					len-=1;
				if(num>9999)
					len-=1;
				if(num>99999)
					len-=1;// Keeps subtracting the larger
                                               // number gets. Works ok for decimals
				gotoXY(1+len+(14*a), 1+(b*2), num);
			}
			else if(Spreadsheet[b+row][a+column].dubl > -1)
			{
				len=6;
				fl = Spreadsheet[b+row][a+column].dubl;
				if(fl > 99.001)
					len-=1;
				if(fl > 999.001)
					len-=1;
				if(fl > 9999.001)
					len-=1;
				if(fl > 99999.001)
					len-=1;
				gotoXY(1+len+(14*a), 1+(b*2));
				cout << fl;
                             // Doesn't work well with doubles
			}
			else if(Spreadsheet[b+row][a+column].text != ".")
			{
				Spreadsheet[b+row][a+column].text.erase( 0, Spreadsheet[b+row][a+column].text.find_first_not_of(' ') );
				len = (Spreadsheet[b+row][a+column].text.length())/2;
				gotoXY((7-len)+(14*a), 1+(b*2), Spreadsheet[b+row][a+column].text);
			}
			if(Spreadsheet[b+row][a+column].function > "")
			{
				Do_Math(Spreadsheet, a+column, b+row);
                               // Above does the math only. No printing
			}
		}
	}
}

How can I center decimal numbers? Or even integers, more efficiently? I have 10 columns across the screen, and 17 rows of cells.

Thanks in advance for anyone's insight and help.
( If anyone would like to see the whole program, I can put it in dropbox, and let you D/L the source. It's 22,000+ bytes )

[Repeater]

At the point of writing the value to the cell, turn the value into a string and then add some spaces to the front of the string.

How many spaces?

(13 - string_length) / 2

That's how many

[JLBorges]

#include <iostream>
#include <iomanip>
#include <sstream>

namespace detail
{
    template < typename T > struct centre
    {
        explicit centre( std::size_t cell_width, const T& value )
            : cell_width(cell_width), value(value) {}
        std::size_t cell_width ;
        const T& value ;
    };

    template < typename T >
    std::ostream& operator<< ( std::ostream& stm, const centre<T>& cntr )
    {
        std::ostringstream str_stm ;
        str_stm.imbue( stm.getloc() ) ;
        str_stm.flags( stm.flags() ) ;
        str_stm.precision( stm.precision() ) ;

        str_stm << cntr.value ;
        const std::string str = str_stm.str() ;
        if( str.size() < cntr.cell_width )
        {
            const auto diff = cntr.cell_width - str.size() ;
            return stm << std::string( diff/2, ' ' ) << str
                       << std::string( (diff+1)/2, ' ' ) ;
        }
        else return stm << str ;
    }
}

template < typename T > detail::centre<T> centre( std::size_t cell_width, const T& value )
{ return detail::centre<T>(cell_width,value) ; }

int main()
{
    std::cout << "|012345678901234567890123456789|\n"
              << '|' << centre( 10, 123 ) << "|\n"
              << '|' << std::showbase << std::hex << centre( 16, 0x123 ) << "|\n"
              << '|' << centre( 25, "hello world!" ) << "|\n"
              << '|' << std::fixed << std::setprecision(2) << std::showpos
              << centre( 12, 12.345 ) << "|\n" ;
}

http://coliru.stacked-crooked.com/a/374470721f73418a

[whitenite1]

@Repeater

I tried what you suggested, but more numbers were being added into the float number being converted. I would enter something like, 123.50, and in would be converted to something like, 123.499009. The number I typed would appear in the spreadsheet cell, but the sting length would come out as the converted second number. I had forgo that idea. Thank you though for your help.

@JLBorges

I copied your namespace and template into my Spreadsheet program. I just had to use the last line in your code, and the float was centered in the cell. Thanks. I'm much happier with my programming endeavor now.

[Repeater]

123.50, and in would be converted to something like, 123.499009.

Actually, I suspect if you entered 123.50 that would not be converted, because a floating point number can store that value.

Nonetheless, time for you to learn about floating point numbers.

Here's the key thing for you to remember; a floating point number CANNOT store every decimal. In fact, it can store almost none of them.

If you try to store the value 123.40 in a floating point number, it WILL NOT store the value 123.40

If you try to store the value 123.41 in a floating point number, it WILL NOT store the value 123.41

You can experiment with it yourself to see what numbers can actually be stored; https://www.h-schmidt.net/FloatConverter/

https://floating-point-gui.de/