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Why does printf specifier format %n not work?

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问题 This is my code: #include <stdio.h> int main(void) { int n; fprintf(stdout, "Hello%n World\n", &n); fprintf(stdout, "n: %d\n", n); return 0; } This is my output: Hellon: 0 Why does the fprintf format specifier "%n" not work? Why is the string to be printed interrupted? ISO/IEC 9899:201x C11 - 7.21.6.1 - The fprintf function The conversion specifiers and their meanings are: (...) %n The argument shall be a pointer to signed integer into which is written the number of characters written to the

Reading character with scanf()

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问题 This code is for game of craps . #include <stdio.h> #include <stdlib.h> #include <stdbool.h> #include <time.h> int roll_dice(void); bool play_game(void); int main() { int i, ch,win = 0,lose = 0; bool flag; srand((unsigned)time(NULL)); do { flag = play_game(); if(flag) { printf("You win!"); win++; } else { printf("You lose!"); lose++; } printf("\n\nPlay again(Y/N)? "); scanf("%c", &ch); ch = getchar(); printf("\n"); }while(ch == 'Y' || ch == 'y'); printf("\nWins: %d Losses: %d",win,lose);

Treating 0 as a significant figure in printf %g format specifier

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问题 I'm trying to print floating point numbers 1.2345678, 0.1234567, 123.45678 using printf in such a way that only the first n characters are printed. I want these number to line up. The %g format specifier in printf("%*g", n, var) does this but the specifier is not treating the 0 in 0.1234567 as a significant figure. This causes the alignment of 0.1234567 to go off wrt to the other two figures. What's the best way to align the numbers in the formats given. Either by treating 0 as significant

Treating 0 as a significant figure in printf %g format specifier

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I'm trying to print floating point numbers 1.2345678, 0.1234567, 123.45678 using printf in such a way that only the first n characters are printed. I want these number to line up. The %g format specifier in printf("%*g", n, var) does this but the specifier is not treating the 0 in 0.1234567 as a significant figure. This causes the alignment of 0.1234567 to go off wrt to the other two figures. What's the best way to align the numbers in the formats given. Either by treating 0 as significant with %g or using some other method? By definition leading zeros are not significant figures. If you want

Should I use an exception specifier in C++?

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In C++, you can specify that a function may or may not throw an exception by using an exception specifier. For example: void foo() throw(); // guaranteed not to throw an exception void bar() throw(int); // may throw an exception of type int void baz() throw(...); // may throw an exception of some unspecified type I'm doubtful about actually using them because of the following: The compiler doesn't really enforce exception specifiers in any rigorous way, so the benefits are not great. Ideally, you would like to get a compile error. If a function violates an exception specifier, I think the

Should I use an exception specifier in C++?

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问题 In C++, you can specify that a function may or may not throw an exception by using an exception specifier. For example: void foo() throw(); // guaranteed not to throw an exception void bar() throw(int); // may throw an exception of type int void baz() throw(...); // may throw an exception of some unspecified type I\'m doubtful about actually using them because of the following: The compiler doesn\'t really enforce exception specifiers in any rigorous way, so the benefits are not great.