The Lisp Reader
The Lisp reader is a program
that reads input in character form and
converts it into Lisp's internal form, including:
- Looking up symbol names to find the pointers to the corresponding
symbol data structures in memory. Lisp
structures within the computer always use pointers rather than names.
The only times Lisp uses the name of a symbol are:
- When reading in the symbol, the Lisp reader looks up the symbol's name
in a symbol table to find the corresponding pointer.
- When printing a symbol, Lisp follows a pointer from the symbol
data structure to the string that is the
symbol's print name and prints it as the
external representation of the symbol.
- Building list structure for parenthesized expressions.
- Ignoring comments.
- Changing ' expr into (quote expr ).
- Performing other transformations of input into
internal forms, e.g. converting numbers from printed form to machine