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 {Driver Loop with Side Effects} Pages 37, 53, 59

This driver loop (Figure N1) is similar to the one in Figure 8 (which didn't work). This one does work because, although top-level procedure definitions are closed in the current top-level environment, that environment is using a side effect when new definitions are made.

For EVAL and EVSETQ see Figure 11. For LOOKUP1 see Figure 3 (not Figure 10, despite Figure 11!).

Figure N1 Implementation of DRIVER-LOOP Using Side Effects