LoadShaderAsString() не определена. Как загрузить код шейдера?

#include <stdlib.h>
#include <stdio.h>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <glm/glm.hpp>

GLuint LoadShaders(const char *vertexshader, const char *fragmentshader)
{
    cout << "Use shaders: " << vertexshader << " " << fragmentshader << endl;
    GLint compile = GL_FALSE;
    int errorInfo = 0;
    GLuint vsID = glCreateShader(GL_VERTEX_SHADER);
    GLuint fsID = glCreateShader(GL_FRAGMENT_SHADER);
 
    string vsCode = "";
    ifstream vsStream(vertexshader, ios::in);
    if (vsStream.is_open())
    {
        string line = "";
        while (getline(vsStream, line))
        {
            vsCode += "\n" + line;
        }
        vsStream.close();
    }
    else 
    {
        cout << "Impossible to open vertex shader file!" << endl;
    }
 
    string fsCode = "";
    ifstream fsStream(fragmentshader, ios::in);
    if (fsStream.is_open())
    {
        string line = "";
        while (getline(fsStream, line))
        {
            fsCode += "\n" + line;
        }   
        fsStream.close();
    }
 
    cout << "Try to compile vertex shader..." << endl;
 
    const char *vsInCode = vsCode.c_str();
 
    glShaderSource(vsID, 1, &vsInCode, NULL);
    glCompileShader(vsID);
    glGetShaderiv(vsID, GL_COMPILE_STATUS, &compile);
    glGetShaderiv(vsID, GL_INFO_LOG_LENGTH, &errorInfo);
    if (errorInfo > 0 || !compile)
    {
        vector<char> vsError(errorInfo + 1);
        glGetShaderInfoLog(vsID, errorInfo, NULL, &vsError[0]);
        cout << &vsError[0] << endl;
    }
    compile = GL_FALSE; 
    errorInfo = 0;
 
    cout << "Try to compile fragment shader..." << endl;
 
    const char *fsInCode = fsCode.c_str();
 
    glShaderSource(fsID, 1, &fsInCode, NULL);
    glCompileShader(fsID);
    glGetShaderiv(fsID, GL_COMPILE_STATUS, &compile);
    glGetShaderiv(fsID, GL_INFO_LOG_LENGTH, &errorInfo);
    if (errorInfo > 0 || !compile)
    {
        vector<char> fsError(errorInfo + 1);
        glGetShaderInfoLog(fsID, errorInfo, NULL, &fsError[0]);
        cout << &fsError[0] << endl;
    }
    
    compile = GL_FALSE; 
    errorInfo = 0;
 
    cout << "Try to link program..." << endl;
    GLuint program = glCreateProgram();
    glAttachShader(program, vsID);
    glAttachShader(program, fsID);
    glLinkProgram(program);
    glGetProgramiv(program, GL_LINK_STATUS, &compile);
    glGetProgramiv(program, GL_INFO_LOG_LENGTH, &errorInfo);
    if (errorInfo > 0  || !compile) 
    {
        vector<char> programError(errorInfo + 1);
        glGetProgramInfoLog(program, errorInfo, NULL, &programError[0]);
        cout << &programError[0] << endl;
    }
 
    glDeleteShader(vsID);
    glDeleteShader(fsID);
 
    return program;
}

GLuint program = LoadShaders("путь к вершинному/vs.vert", "путь к фрагментному/fs.frag");