Running Pre-Scheme as Scheme
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To facilitate the operation of Pre-Scheme systems within a high-level Scheme development environment, Scheme48 simply defines the prescheme, ps-memory, ps-record-types, ps-flonums, and ps-receive structures in terms of Scheme; Pre-Scheme structures can be loaded as regular Scheme structures because of this.  Those structures and the interfaces they implement are defined in the files scheme/prescheme/interface.scm and scheme/prescheme/package-defs.scm from the main Scheme48 distribution; simply load these files into the Module commands, config package before loading any Pre-Scheme configuration files.

The Pre-Scheme emulation layer in Scheme has some shortcomings:

  * No more than sixteen megabytes can be allocated at once.

  * More than thirty-two or sixty-four or so allocations result in addresses overflowing bignums, which deallocations does not affect.

  * Flonum memory access is unimplemented.  (Flonum arithmetic works, though.)

  * The layer is very slow.