6.34.3 Additional hash functions

Function: bytevector-hash bv

Function: bytevector-hash bv max-len

Return a non–negative fixnum representing the hash value for bv, based on its current contents. When creating hash tables using bytevectors as keys: this hash function is suitable for use with bytevector=? as an equivalence function.

About the max-len argument:

• When max-len is a non–negative fixnum: it is the maximum number of bytes to use to compute the hash value, starting from the beginning of bv. If the length of bv is greater than max-len: only the first max-len bytes are used. If the length of bv is less than or equal to max-len: all the bytes in bv are used.
• When max-len is #f or not present: if the length of bv is greater than 256 bytes, only the first 256 bytes are used to compute the hash.
• When max-len is #t: all the bytes in bv are used.

NOTE When the hash value is computed using a number of bytes N less than the bytevector length: applications must not assume that two bytevectors having the first N bytes equal will have the same hash value.

Function: vector-hash vec

Function: vector-hash vec max-len

Return a non–negative fixnum representing the hash value for vec, based on its current contents. When creating hash tables using vectors as keys: this hash function is suitable for use with vector=? as an equivalence function.

About the max-len argument:

• When max-len is a non–negative fixnum: it is the maximum number of items to use to compute the hash value, starting from the beginning of vec. If the length of vec is greater than max-len: only the first max-len items are used. If the length of vec is less than or equal to max-len: all the items in vec are used.
• When max-len is #f or not present: if the length of vec is greater than 3 items, only the first 3 items are used to compute the hash.
• When max-len is #t: all the items in vec are used.

NOTE When the hash value is computed using a number of items N less than the vector length: applications must not assume that two vectors having the first N items equal will have the same hash value.

Function: list-hash ell

Function: list-hash ell max-len

Return a non–negative fixnum representing the hash value for ell, based on its current contents. When creating hash tables using lists as keys: this hash function is suitable for use with equal? as an equivalence function.

About the max-len argument:

• When max-len is a non–negative fixnum: it is the maximum number of items to use to compute the hash value, starting from the beginning of ell. If the length of ell is greater than max-len: only the first max-len items are used. If the length of ell is less than or equal to max-len: all the items in ell are used.
• When max-len is #f or not present: if the length of ell is greater than 3 items, only the first 3 items are used to compute the hash.
• When max-len is #t: all the items in ell are used.

NOTE When the hash value is computed using a number of items N less than the list length: applications must not assume that two lists having the first N items equal will have the same hash value.

Function: pair-hash pair

Function: ipair-hash ipair

Hash functions for pairs and immutable pairs.

Function: char-hash ch

Function: char-ci-hash ch

Hash function for characters. char-ci-hash first applies char-foldcase to ch.

Function: boolean-hash bool

Hash function for booleans.

Function: fixnum-hash fx

Hash function for fixnums.

Function: bignum-hash bn

Hash function for bignums.

Function: exact-integer-hash N

Hash function for exact integers, fixnums and bignums.

Function: flonum-hash fl

Hash function for flonums.

Function: ratnum-hash rn

Hash function for ratnums.

Function: cflonum-hash cfl

Hash function for cflonums.

Function: flonum-hash fl

Hash function for flonums.

Function: compnum-hash Z

Hash function for compnum objects.

Function: struct-hash stru

Hash function for Vicare structs. This is a very low quality hash function.

NOTE The result returned by this hash function depends on the values in the struct fields, so: it will change if the struct is mutated.

Function: record-hash reco

Hash function for R6RS records. This is a very low quality hash function. Notice that it does not use the custom hash function of reco (if any).

NOTE The result returned by this hash function depends on the values in the record fields, so: it will change if the record is mutated.

Function: enum-set-hash es

Hash function for enumeration sets.

Function: pointer-hash ptr

Return a fixnum representing the hash value of ptr.

Function: promise-hash prom

Hash function for promise objects.

Function: void-hash obj

Function: eof-object-hash obj

Function: would-block-hash obj

Function: sentinel-hash obj

Ignore obj and return a non–negative exact integer representing the hash value for (void), (eof-object), (would-block-object) and (sentinel).

Function: object-hash obj

Hash function for any Scheme object. For some object types: this is a very low quality hash function.

When obj is a record whose record–type defines a custom hash function: object-hash makes use of such custom function; otherwise record-hash is used.

Function: pointer-value obj

This is used by eq? hashtables to obtain a fixnum from references to objects that are meant to be compared with eq?.