number matrix

Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 11 Exercise 15
Using std_lib_facilities.h by Bjarne Stroustrup.

[code language=”cpp”]
// Philipp Siedler
// Bjarne Stroustrup’s PPP
// Chapter 11 Exercise 15

#include "std_lib_facilities.h"

int main()
try
{
cout << "enter name for input file" << endl;
string iname = "input/";
string itemp;
cin >> itemp;
iname += itemp;
ifstream ifs{ iname };
if (!ifs) { cout << "could not open input file." << endl; }

cout << "enter name for output file" << endl;
string oname = "output/";
string otemp;
cin >> otemp;
oname += otemp;
ofstream ofs{ oname };
if (!ofs) { cout << "could not open output file." << endl; }

int width = 20;
int counter = 0;

for (double d; ifs >> d;) {
ofs << setw(width) << scientific << d;
counter++;
if (counter == 4) {
ofs << endl;
counter = 0;
}
}

keep_window_open();
}
catch (runtime_error e) {
cout << e.what() << endl;
keep_window_open();
}
catch (…) {
cout << "Exiting" << endl;
keep_window_open();
}
[/code]

Output:
enter name for input file
p409_15_random_num.txt
enter name for output file
p409_15_random_num_out.txt

Input-File: p409_15_random_num.txt
58
32
50
80
54
13
24
82
52
17
17
8
87
12
35
42
88
72
46
91
69
60
84
55
99
21
6
25
53
13
75
83
94
2
71
35
85
50
71
99
60
47
68
29
100
54
45
66
4
98
57
13
23
3
8
9
47
67
17
52
5
60
73
28
18
45
5
7
99
78
78
17
3
87
37
33
83
92
83
99
45
75
28
73
66
44
11
73
9
24
29
39
52
99
24
95
8
91
90
99

Input-File: p409_15_random_num_out.txt
       5.800000e+01        3.200000e+01        5.000000e+01        8.000000e+01
        5.400000e+01        1.300000e+01        2.400000e+01        8.200000e+01
        5.200000e+01        1.700000e+01        1.700000e+01        8.000000e+00
        8.700000e+01        1.200000e+01        3.500000e+01        4.200000e+01
        8.800000e+01        7.200000e+01        4.600000e+01        9.100000e+01
        6.900000e+01        6.000000e+01        8.400000e+01        5.500000e+01
        9.900000e+01        2.100000e+01        6.000000e+00        2.500000e+01
        5.300000e+01        1.300000e+01        7.500000e+01        8.300000e+01
        9.400000e+01        2.000000e+00        7.100000e+01        3.500000e+01
        8.500000e+01        5.000000e+01        7.100000e+01        9.900000e+01
        6.000000e+01        4.700000e+01        6.800000e+01        2.900000e+01
        1.000000e+02        5.400000e+01        4.500000e+01        6.600000e+01
        4.000000e+00        9.800000e+01        5.700000e+01        1.300000e+01
        2.300000e+01        3.000000e+00        8.000000e+00        9.000000e+00
        4.700000e+01        6.700000e+01        1.700000e+01        5.200000e+01
        5.000000e+00        6.000000e+01        7.300000e+01        2.800000e+01
        1.800000e+01        4.500000e+01        5.000000e+00        7.000000e+00
        9.900000e+01        7.800000e+01        7.800000e+01        1.700000e+01
        3.000000e+00        8.700000e+01        3.700000e+01        3.300000e+01
        8.300000e+01        9.200000e+01        8.300000e+01        9.900000e+01
        4.500000e+01        7.500000e+01        2.800000e+01        7.300000e+01
        6.600000e+01        4.400000e+01        1.100000e+01        7.300000e+01
        9.000000e+00        2.400000e+01        2.900000e+01        3.900000e+01
        5.200000e+01        9.900000e+01        2.400000e+01        9.500000e+01
        8.000000e+00        9.100000e+01        9.000000e+01        9.900000e+01