カテゴリー: C++

#include <cppstd.h>

int main() {
    int i, a[10];

    for (i = 1; i<=10; i++){
        a[i] = 0;
        cout << "i = " << i << endl;
    }

    return 0;
}
--------------------------------------------------
出力
--------------------------------------------------
i = 1
i = 2
i = 3
i = 4
i = 5
i = 6
i = 7
i = 8
i = 9
i = 10
Abort trap: 6

#include <cppstd.h>

int main() {
    char *p;

    p = nullptr;
    printf("Location 0 contains %d\n", *p);

    return 0;
}
--------------------------------------------------
出力
--------------------------------------------------
Segmentation fault: 11

#include <cppstd.h>
#include <test2.h>

char hello[] = "hello";

int main() {

    show();

    return 0;
}

#include <cppstd.h>

// extern char hello[]; // 正しくはこちら
extern char *hello;

void show() {

    printf("%s\n",hello);

}

Bus error: 10

//正常であれば
hello

#include <cppstd.h>
#include <malloc/malloc.h>

int main() {
    char* s = "abc";
    char* t = "def";
    char* r1;
    char* r2;
    char* r3;

    cout << "strlen(s) " << to_string(strlen(s)) << endl;
    cout << "strlen(t) " << to_string(strlen(t)) << endl;

    r1 = (char*)malloc(strlen(s) + strlen(t) +1);
    r2 = (char*)malloc(0);
    r3 = (char*)malloc(10000);

    int size1 = malloc_size(r1); 
    int size2 = malloc_size(r2); 
    int size3 = malloc_size(r3);

    cout << "r1で確保されたサイズ " << to_string(size1) << endl;
    cout << "r2で確保されたサイズ " << to_string(size2) << endl;
    cout << "r3で確保されたサイズ " << to_string(size3) << endl;

    strcat(r1, s);
    strcat(r1, t);

    cout << "r1 " << r1 << endl;

    free(r1);
    free(r2);
    free(r3);

    return 0;
}
--------------------------------------------------
出力
--------------------------------------------------
strlen(s) 3
strlen(t) 3
r1で確保されたサイズ 16
r2で確保されたサイズ 16
r3で確保されたサイズ 10240
r1 abcdef

int main() {
    string str1 = 'a';
    string str2 = 'abc';

    cout << "str1 " << str1 << endl;
    cout << "str2 " << str2 << endl;

    printf('a\n');

    return 0;
}
--------------------------------------------------
コンパイルエラー内容
--------------------------------------------------
src/test.cpp:4:12: error: no viable conversion from 'char' to 'std::string' (aka 'basic_string<char>')
    string str1 = 'a';
           ^      ~~~
src/test.cpp:5:12: error: no viable conversion from 'int' to 'std::string' (aka 'basic_string<char>')
    string str2 = 'abc';
           ^      ~~~~~
src/test.cpp:10:5: error: no matching function for call to 'printf'
    printf('a\n');
    ^~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/stdio.h:170:6: note: candidate function not viable: no known conversion from 'int' to 'const char *' for 1st argument
int      printf(const char * __restrict, ...) __printflike(1, 2);
         ^

#include <cppstd.h>

string toBinary(int n)
{
    string r;
    while (n != 0){
        r = ( n % 2 == 0 ? "0" : "1" ) + r; // 参考サイトでは末尾に結合(正しくは先頭に結合)
        cout << "r: " << r.c_str() << endl;
        n /= 2;
    }
    return r;
}

int main() {
    int number = 50;
    
    string bin = toBinary(number);

    cout << "decimal: " << number << endl;
    cout << "binary : " << bin << endl;

    return 0;
}
--------------------------------------------------
出力
--------------------------------------------------
r: 0
r: 10
r: 010
r: 0010
r: 10010
r: 110010
decimal: 50
binary : 110010

int main()
{   
    int x = 50;
    int x2, x3;
    int i2;
    bool finished = false; 

    int i = 0;
    vector<int> pow_list; 
    while(1){
        int num1 = std::pow(2, i);
        cout << "num1 " << num1 << endl;
        if (num1 > x){
            pow_list.push_back(i-1);
            x2 = x - pow(2,i-1);
            cout << "x2 " << x2 << endl;

            
            while(1){
                int num2 = std::pow(2, i2);
                cout << "num2 " << num2 << endl;
                if (num2 > x2){
                    pow_list.push_back(i2-1);
                    x3 = x2 - pow(2,i2-1);
                    cout << "x3 " << x3 << endl;

                    finished = true;
                    break;
                } else {
                    i2 += 1;
                }
            }
        } else {
            i += 1;
        }

        if (finished) {
            break;
        }

    }

    cout << "i " << i << endl;
    cout << "i2 " << i2 << endl;
}
--------------------------------------------------
出力
--------------------------------------------------
num1 1
num1 2
num1 4
num1 8
num1 16
num1 32
num1 64
x2 18
num2 1
num2 2
num2 4
num2 8
num2 16
num2 32
x3 2 // 50から2^5と2^4を引いた残り
i 6 // 2^6は64なので50から最初に引く数字は2^5=32
i2 5 // 次に50-32=18から2^4=16を引く

// したがって50の内訳は2^5+2^4+2^1

int main()
{   
    int x = 010;
    int y = 50;

    int z = x + y;

    printf("z = %d\n",z);
}
--------------------------------------------------
出力
--------------------------------------------------
z = 58

int main()
{   
    int x = 0x1F;
    int y = 50;

    int z = x + y;

    printf("z = %d\n",z);
}
--------------------------------------------------
出力
--------------------------------------------------
z = 81

// 間違ったコード
int main()
{   
    int x;
    int y = 50;
    int* ptr;

    ptr = &x;
    *ptr = 20;

    auto z = y/*ptr;

    printf("z = %d\n",z);

}
--------------------------------------------------
出力
--------------------------------------------------
src/test.cpp:13:15: error: unterminated /* comment
    auto z = y/*ptr;
              ^
src/test.cpp:13:15: error: expected ';' at end of declaration
    auto z = y/*ptr;
              ^
              ;
src/test.cpp:17:2: error: expected '}'
}
 ^
src/test.cpp:5:1: note: to match this '{'
{   
^
3 errors generated.

// 正しいコード
int main()
{   
    int x;
    int y = 50;
    int* ptr;

    ptr = &x;
    *ptr = 20;

    auto z = y/ *ptr;
    // あるいは
    // auto z = y/(*ptr);

    printf("z = %d\n",z);

}
--------------------------------------------------
出力
--------------------------------------------------
z = 2

#include <iostream>
#include <vector>

int num0;

int main()
{
    int num1;
    int num2 = 3;

    int *ary;
    ary = new int[5];

    std::vector<int> vec = {1,2,3};
    
    std::cout << "num0 " << &num0 << std::endl;
    std::cout << "num1 " << &num1 << std::endl;
    std::cout << "num2 " << &num2 << std::endl;
    std::cout << "ary  " << &ary << std::endl;
    std::cout << "vec  " << &vec << std::endl;
    std::cout << "vec.max_size() " << vec.max_size() << std::endl;
    
}
--------------------------------------------------
出力例
--------------------------------------------------
num0 0x1048e4128
num1 0x16b5236a8
num2 0x16b5236a4
ary  0x16b523698
vec  0x16b523680
vec.max_size() 4611686018427387903