The project Build described in section 8.2.4 is based on the Surface_Build subclass of Surface. Surface_Build adds an instance variable build_parm of class Build_Parm used for storing the description of surface patches to its superclass Surface.
Surface_Build is only available when the Build project is added -- either interactively via the button in the manag menu or by calling g_project_add or g_project_use.
The type SURFACE_BUILD is not part of the GRAPE header file grape.h, but it isn't needed anyway. Methods should be implemented for the superclass Surface, if you really have to write a method for Surface_Build you can use SURFACE instead.
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