問題與std :: stoi，沒有在MinGW GCC 5.1.0上聲明

Question

我在我的電腦上運行MinGW GCC 5.1.0的代碼。

當我輸入：

g++ hope.cpp -o hope -I D:\armadillo-7.600.2\include 

在CMD告訴我：

hope.cpp:183:26: error: 'stoi' was not declared in this scope 
Point_Num = stoi(temp[1]);//number of point 
        ^
hope.cpp:190:34: error: 'stof' was not declared in this scope 
Point(i, 0) = stof(temp[travel]); 

但是，當我進入：

g++ hope.cpp -o hope -I D:\armadillo-7.600.2\include -std=c++11 

在CMD告訴我：

C:\Users\von77\AppData\Local\Temp\ccXdhQzS.o:hope.cpp：(.text$_ZN4arma7op_norm21vec_norm_1_direct_stdIdEET_RKNS_3MatIS2_EE[_ZN4arma7op_norm21vec_norm_1_direct_stdIdEET_RKNS_3MatIS2_EE]+0x7b): undefined reference to `dasum_' 
C:\Users\von77\AppData\Local\Temp\ccXdhQzS.o:hope.cpp:(.text$_ZN4arma7op_norm21vec_norm_2_direct_stdIdEET_RKNS_3MatIS2_EE[_ZN4arma7op_norm21vec_norm_2_direct_stdIdEET_RKNS_3MatIS2_EE]+0x7f): undefined reference to `dnrm2_' 
C:\Users\von77\AppData\Local\Temp\ccXdhQzS.o:hope.cpp:(.text$_ZN4arma4blas3dotIdEET_yPKS2_S4_[_ZN4arma4blas3dotIdEET_yPKS2_S4_]+0x3f): undefined reference to `ddot_' 
C:\Users\von77\AppData\Local\Temp\ccXdhQzS.o:hope.cpp:(.text$_ZN4arma6lapack5gesddIdEEvPcPiS3_PT_S3_S5_S5_S3_S5_S3_S5_S3_S3_S3_[_ZN4arma6lapack5gesddIdEEvPcPiS3_PT_S3_S5_S5_S3_S5_S3_S5_S3_S3_S3_]+0x8c): undefined reference to `dgesdd_' 
collect2.exe: error: ld returned 1 exit status 

我用atoi代替stoi後： 我得到了與「g ++ hope.cpp -o hope -I D：\ armadillo-7.600.2 \ include -std = C++ 11」相同的結果。

Answer 1

你需要包含字符串頭

#include <string> 

，你需要指定命名空間

std::stoi(temp[1]);