8.16.0.4
Property that automatically adds an implementation of the
prop:equal+hash property. If the property value is
#t, the
automatically generated equality predicate and hash code functions use all of
the struct type’s fields. If the property value is a list, then the equality
predicate and hash code functions use only the fields with the indexes in the
list.
In addition to the indicated fields, the hash code function also depends on a
random seed and the name of the struct type. A new random seed is generated for
each instantiation of the scramble/struct module.
If prop:auto-equal+hash is attached to a struct type that has a super
struct type, then the super struct type must also have the
prop:auto-equal+hash, and the new equality and hash code functions
extend the super type’s functions. If the super struct type does not have the
prop:auto-equal+hash property, an error is raised.
In the following example, the equality and hash code functions of the
point3 struct type use only the z field out of
point3’s fields, disregarding the color field, but they also
use both of point’s fields.
|
| > (equal? (point3 1 2 3 #f) | | (point3 1 2 3 'red)) |
|
#t |
| > (equal? (point3 0 0 3 'red) | | (point3 1 2 3 'red)) |
|
#f |
|
#t |