You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
14 lines
840 B
14 lines
840 B
|
|
Exercise 2.78: The internal procedures in the
|
|
scheme-number package are essentially nothing more than calls to the
|
|
primitive procedures +, -, etc. It was not possible to use the
|
|
primitives of the language directly because our type-tag system requires that
|
|
each data object have a type attached to it. In fact, however, all Lisp
|
|
implementations do have a type system, which they use internally. Primitive
|
|
predicates such as symbol? and number? determine whether data
|
|
objects have particular types. Modify the definitions of type-tag,
|
|
contents, and attach-tag from 2.4.2 so that our
|
|
generic system takes advantage of Scheme’s internal type system. That is to
|
|
say, the system should work as before except that ordinary numbers should be
|
|
represented simply as Scheme numbers rather than as pairs whose car is
|
|
the symbol scheme-number.
|
|
|