Re: [問題] 九九乘法表不用迴圈是叫我直接從1列到81?

[PkmX (阿貓)]

http://coliru.stacked-crooked.com/a/fba5b7b3b253288d

#include <iostream>
#include <string>

struct table {
    std::string s;

    table() {}
    ~table() { std::cout << this->s; }
    table(const int n) : s{std::to_string(n)} {}
    table(std::string&& s_) : s{std::move(s_)} {}
    table(table&& other) : s{other.take()} {}
    table operator=(const int n) { return this->take() + " = " + std::to_string(n); }
    table operator=(table&& rhs) { return this->take() + " = " + rhs.take(); }

    std::string take() { const auto s = this->s; this->s.clear(); return s; }
    bool empty() const { return this->s.empty(); }
    const char& back() const { return this->s.back(); }
};

table operator++(table&& t, int) { return t.take(); }
table operator--(table&& t, int) { return t.take(); }
table operator-(table&& lhs, table&& rhs) { return lhs.take() + rhs.take(); }
table operator*(table&& lhs, table&& rhs) { return lhs.take() + " x " + rhs.take(); }
table operator||(table&& lhs, table&& rhs) { return lhs.take() + "\t" + rhs.take(); }
table operator|(table&& lhs, table&& rhs)
{ return lhs.empty() || lhs.back() == '\n' ? lhs.take() + rhs.take() : lhs.take() + "\n" + rhs.take(); }
table operator/(table&& lhs, table&& rhs) { return lhs.take() + "\n\n" + rhs.take(); }

#define x * (table)
#define o table{}

int main() {
    o-------------------------------------------------------o
    | 2 x 1 =  2 || 3 x 1 =  3 || 4 x 1 =  4 || 5 x 1 =  5  \
    | 2 x 2 =  4 || 3 x 2 =  6 || 4 x 2 =  8 || 5 x 2 = 10  \
    | 2 x 3 =  6 || 3 x 3 =  9 || 4 x 3 = 12 || 5 x 3 = 15  \
    | 2 x 4 =  8 || 3 x 4 = 12 || 4 x 4 = 16 || 5 x 4 = 20  \
    | 2 x 5 = 10 || 3 x 5 = 15 || 4 x 5 = 20 || 5 x 5 = 25  \
    | 2 x 6 = 12 || 3 x 6 = 18 || 4 x 6 = 24 || 5 x 6 = 30  \
    | 2 x 7 = 14 || 3 x 7 = 21 || 4 x 7 = 28 || 5 x 7 = 35  \
    | 2 x 8 = 16 || 3 x 8 = 24 || 4 x 8 = 32 || 5 x 8 = 40  \
    | 2 x 9 = 18 || 3 x 9 = 27 || 4 x 9 = 36 || 5 x 9 = 45  /
    o------------++------------++------------++-------------o
    | 6 x 1 =  6 || 7 x 1 =  7 || 8 x 1 =  8 || 9 x 1 =  9  \
    | 6 x 2 = 12 || 7 x 2 = 14 || 8 x 2 = 16 || 9 x 2 = 18  \
    | 6 x 3 = 18 || 7 x 3 = 21 || 8 x 3 = 24 || 9 x 3 = 27  \
    | 6 x 4 = 24 || 7 x 4 = 28 || 8 x 4 = 32 || 9 x 4 = 36  \
    | 6 x 5 = 30 || 7 x 5 = 35 || 8 x 5 = 40 || 9 x 5 = 45  \
    | 6 x 6 = 36 || 7 x 6 = 42 || 8 x 6 = 48 || 9 x 6 = 54  \
    | 6 x 7 = 42 || 7 x 7 = 49 || 8 x 7 = 56 || 9 x 7 = 63  \
    | 6 x 8 = 48 || 7 x 8 = 56 || 8 x 8 = 64 || 9 x 8 = 72  \
    | 6 x 9 = 54 || 7 x 9 = 63 || 8 x 9 = 72 || 9 x 9 = 81  /
    o-------------------------------------------------------o;
}

------------------------------------------------------------------------------

$ g++ -std=c++17 -Wall -Wextra -pedantic -O2 -Wno-parentheses main.cpp && ./a.out
2 x 1 = 2       3 x 1 = 3       4 x 1 = 4       5 x 1 = 5
2 x 2 = 4       3 x 2 = 6       4 x 2 = 8       5 x 2 = 10
2 x 3 = 6       3 x 3 = 9       4 x 3 = 12      5 x 3 = 15
2 x 4 = 8       3 x 4 = 12      4 x 4 = 16      5 x 4 = 20
2 x 5 = 10      3 x 5 = 15      4 x 5 = 20      5 x 5 = 25
2 x 6 = 12      3 x 6 = 18      4 x 6 = 24      5 x 6 = 30
2 x 7 = 14      3 x 7 = 21      4 x 7 = 28      5 x 7 = 35
2 x 8 = 16      3 x 8 = 24      4 x 8 = 32      5 x 8 = 40
2 x 9 = 18      3 x 9 = 27      4 x 9 = 36      5 x 9 = 45

6 x 1 = 6       7 x 1 = 7       8 x 1 = 8       9 x 1 = 9
6 x 2 = 12      7 x 2 = 14      8 x 2 = 16      9 x 2 = 18
6 x 3 = 18      7 x 3 = 21      8 x 3 = 24      9 x 3 = 27
6 x 4 = 24      7 x 4 = 28      8 x 4 = 32      9 x 4 = 36
6 x 5 = 30      7 x 5 = 35      8 x 5 = 40      9 x 5 = 45
6 x 6 = 36      7 x 6 = 42      8 x 6 = 48      9 x 6 = 54
6 x 7 = 42      7 x 7 = 49      8 x 7 = 56      9 x 7 = 63
6 x 8 = 48      7 x 8 = 56      8 x 8 = 64      9 x 8 = 72
6 x 9 = 54      7 x 9 = 63      8 x 9 = 72      9 x 9 = 81

靈感來源：
Multi-Dimensional Analog Literals
http://www.eelis.net/C++/analogliterals.xhtml

--
※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 140.113.193.217
※ 文章網址: https://www.ptt.cc/bbs/C_and_CPP/M.1531774190.A.3C0.html
推 cutekid: 猛猛的!
→ MOONRAKER: 太棒了這樣code和document和result都合一了(?)
→ shadow0326: specification by example
→ Schottky: 所見即所得
推 lucky1lk: 強 給推 未必有人看得懂XDDD
推 descent: 看不懂
推 BlazarArc: XDDDDDDDDDD
推 lc85301: 猛XDD
推 dou0228: 比 template 好懂多了 XDD