数据类型转换教程.doc

数据类型转换 一、隐式类型转换 1）简单数据类型 (1)算术运算 转换为最宽的数据类型 eg: [cpp] view plain copy #include iostream using std::cout; using std::endl; int main(int argc, char* argv[]) { int ival = 3; double dval = 3.14159; cout ival + dval endl;//ival被提升为double类型 return 0; } 其运行结果： 6.14159 int main(int argc, char* argv[]) { 010D17D0 push ebp 010D17D1 mov ebp,esp 010D17D3 sub esp,0DCh 010D17D9 push ebx 010D17DA push esi 010D17DB push edi 010D17DC lea edi,[ebp-0DCh] 010D17E2 mov ecx,37h 010D17E7 mov eax,0CCCCCCCCh 010D17EC rep stos dword ptr es:[edi] int ival = 3; 010D17EE mov dword ptr [ival],3 double dval = 3.14159; 010D17F5 movsd xmm0,mmword ptr [__real@400921f9f01b866e (010D6B30h)] 010D17FD movsd mmword ptr [dval],xmm0 cout ival + dval endl;//ival被提升为double类型 010D1802 mov esi,esp 010D1804 push offset std::endlchar,std::char_traitschar (010D1064h) 010D1809 cvtsi2sd xmm0,dword ptr [ival] 010D180E addsd xmm0,mmword ptr [dval] 010D1813 mov edi,esp 010D1815 sub esp,8 010D1818 movsd mmword ptr [esp],xmm0 010D181D mov ecx,dword ptr [_imp_?cout@std@@3V?$basic_ostream@DU?$char_traits@D@std@@@1@A (010D90A8h)] 010D1823 call dword ptr [__imp_std::basic_ostreamchar,std::char_traitschar ::operator (010D90A0h)] 010D1829 cmp edi,esp 010D182B call __RTC_CheckEsp (010D111Dh) 010D1830 mov ecx,eax 010D1832 call dword ptr [__imp_std::basic_ostreamchar,std::char_traitschar ::operator (010D90A4h)] 010D1838 cmp esi,esp 010D183A call __RTC_CheckEsp (010D111Dh) return 0; 010D183F xor eax,eax } 010D1841 pop edi } 010D1842 pop esi 010D1843 pop ebx 010D1844 add esp,0DCh 010D184A cmp ebp,esp 010D184C call __RTC_CheckEsp (010