Common Lisp Implementation

• Use C malloc() to allocate CL Objects
• Use the Boehm-Demers-Weiser conservative garbage collector to reclaim memory of dead objects.

Environment consists:

• Bindings for special variables
• Tags for catch used by throw
• exit points defined by tagbody and block
• entries for unwind-protect
• Signal handlers and restarts

Dynamic environment can be allocated on the heap as a linked list of entries. However,

• catch and throw can be implemented using block and return-from.
• Signal handlers and restarts (i.e. the entire condition system) can be implemented using special variables.

Unwinding the stack (throw, go, return-from) can be implemented using setjmp/longjmp. (See man page)

for built-in data type.

• Fixnums, bignums, ratios, floats, complex numbers
• Characters
• Symbols, packages.
• Conses, arrays, hash tables
• Streams

Its complicated. So two options:

• Write a subset of the reader in C. Replace with a full reader written in Common Lisp later.
• Write the final reader in C, but leave out complicated standard reader macros that can be written CL later

(Same as 1.4)

Several possible implementations:

• A direct interpreter written in C
• A compiler generating native machine code
• A compiler generating byte codes, combined with a byte-code interpreter written in C.