1.4 Language differences
merge-hash-ids
Function
Summary
Returns a hash ID created by merging two hash IDs.
Signature
merge-hash-ids id1 id2 #key ordered => merged-id
Arguments
- id1
- An instance of
<integer>. - id2
- An instance of
<integer>. - ordered
- An instance of
<boolean>. Default value:#f.
Values
- merged-id
- An instance of
<integer>.
Description
Computes a new hash ID by merging the argument hash IDs in some implementation-dependent way. This can be used, for example, to generate a hash ID for an object by combining hash IDs of some of its parts.
The id1, id2 arguments and the return value merged-id are all integers.
The ordered argument is a boolean, and determines whether the algorithm used to the merge the IDs is permitted to be order-dependent. If false (the default), the merged result must be independent of the order in which the arguments are provided. If true, the order of the arguments matters because the algorithm used need not be either commutative or associative. It is best to provide a true value for ordered when possible, as this may result in a better distribution of hash IDs. However, ordered must only be true if that will not cause the hash function to violate the second constraint on hash functions, described on page 123 of the DRM.