/tmp/cce2kj11.o: In function `TimeStep(int)':
l8.cpp:(.text+0x13): undefined reference to `glutTimerFunc'
/tmp/cce2kj11.o: In function `gldraw()':
l8.cpp:(.text+0x2a): undefined reference to `glClear'
l8.cpp:(.text+0x3f): undefined reference to `glColor3f'
l8.cpp:(.text+0x49): undefined reference to `glBegin'
l8.cpp:(.text+0x59): undefined reference to `glVertex2f'
l8.cpp:(.text+0x6e): undefined reference to `glVertex2f'
l8.cpp:(.text+0x7e): undefined reference to `glVertex2f'
l8.cpp:(.text+0x93): undefined reference to `glVertex2f'
/tmp/cce2kj11.o: In function `TimeStep(int)':
l8.cpp:(.text+0x1c): undefined reference to `glutPostRedisplay'
/tmp/cce2kj11.o: In function `gldraw()':
l8.cpp:(.text+0x9c): undefined reference to `glEnd'
/tmp/cce2kj11.o: In function `main':
l8.cpp:(.text.startup+0xe): undefined reference to `glutInit'
l8.cpp:(.text.startup+0x15): undefined reference to `glutInitDisplayMode'
l8.cpp:(.text.startup+0x1e): undefined reference to `glutInitWindowPosition'
l8.cpp:(.text.startup+0x2d): undefined reference to `glutInitWindowSize'
l8.cpp:(.text.startup+0x44): undefined reference to `glClearColor'
l8.cpp:(.text.startup+0x50): undefined reference to `glutCreateWindow'
l8.cpp:(.text.startup+0x5a): undefined reference to `glClear'
l8.cpp:(.text.startup+0x66): undefined reference to `glutDisplayFunc'
l8.cpp:(.text.startup+0x79): undefined reference to `glutTimerFunc'
l8.cpp:(.text.startup+0x7e): undefined reference to `glutMainLoop'
collect2: error: ld returned 1 exit status