title: How to add directives in OpenGL/GLES shaders?
body: <p>Basically I want to create one file which contains my vertex shader as well as fragment shader.</p>
  
  <p>like this.</p>
  
  <pre><code>    #ifdef VERTEX
      attribute vec4  a_pos; 
      attribute vec2   a_texCoords; 
      uniform mat4 combined;  
      varying vec2 v_texCoords; 
           void main(){ 
              v_texCoords =   a_texCoords; 
              gl_Position =  combined *   a_pos; 
          }
      #endif
  
      #ifdef FRAGMENT
       varying vec2 v_texCoords; 
       uniform sampler2D u_texture;
      void main() {
          gl_FragColor = texture2D(u_texture, v_texCoords);
          //gl_FragColor = vec4(1,0,0,1);
      }
      #endif
  </code></pre>
  
  <p>but How to pass directives while compiling the shader like make_file in c/c++?</p>