code: def add_f77_to_env(env):
      
      try:
          F77Suffixes = env['F77FILESUFFIXES']
      except KeyError:
          F77Suffixes = ['.f77']
  
      #print("Adding %s to f77 suffixes" % F77Suffixes)
      try:
          F77PPSuffixes = env['F77PPFILESUFFIXES']
      except KeyError:
          F77PPSuffixes = []
  
      DialectAddToEnv(env, "F77", F77Suffixes, F77PPSuffixes)
docs: Add Builders and construction variables for f77 to an Environment.