diff options
| -rw-r--r-- | pod/perlfunc.pod | 33 | ||||
| -rw-r--r-- | pod/perlguts.pod | 10 |
2 files changed, 28 insertions, 15 deletions
diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod index 2d1e1dfa42..8852b1829c 100644 --- a/pod/perlfunc.pod +++ b/pod/perlfunc.pod @@ -1047,9 +1047,13 @@ element in the hash. (Note: Keys may be C<"0"> or C<"">, which are logically false; you may wish to avoid constructs like C<while ($k = each %foo) {}> for this reason.) -Entries are returned in an apparently random order. When the hash is -entirely read, a null array is returned in list context (which when -assigned produces a FALSE (C<0>) value), and C<undef> in +Entries are returned in an apparently random order. The actual random +order is subject to change in future versions of perl, but it is guaranteed +to be in the same order as either the C<keys()> or C<values()> function +would produce on the same (unmodified) hash. + +When the hash is entirely read, a null array is returned in list context +(which when assigned produces a FALSE (C<0>) value), and C<undef> in scalar context. The next call to C<each()> after that will start iterating again. There is a single iterator for each hash, shared by all C<each()>, C<keys()>, and C<values()> function calls in the program; it can be reset by @@ -1064,7 +1068,7 @@ only in a different order: print "$key=$value\n"; } -See also C<keys()> and C<values()>. +See also C<keys()>, C<values()> and C<sort()>. =item else BLOCK @@ -1985,9 +1989,11 @@ See L</split>. Returns a list consisting of all the keys of the named hash. (In a scalar context, returns the number of keys.) The keys are returned in -an apparently random order, but it is the same order as either the -C<values()> or C<each()> function produces (given that the hash has not been -modified). As a side effect, it resets HASH's iterator. +an apparently random order. The actual random order is subject to +change in future versions of perl, but it is guaranteed to be the same +order as either the C<values()> or C<each()> function produces (given +that the hash has not been modified). As a side effect, it resets +HASH's iterator. Here is yet another way to print your environment: @@ -2017,14 +2023,16 @@ an array by assigning a larger number to $#array.) If you say keys %hash = 200; -then C<%hash> will have at least 200 buckets allocated for it--256 of them, in fact, since -it rounds up to the next power of two. These +then C<%hash> will have at least 200 buckets allocated for it--256 of them, +in fact, since it rounds up to the next power of two. These buckets will be retained even if you do C<%hash = ()>, use C<undef %hash> if you want to free the storage while C<%hash> is still in scope. You can't shrink the number of buckets allocated for the hash using C<keys()> in this way (but you needn't worry about doing this by accident, as trying has no effect). +See also C<each()>, C<values()> and C<sort()>. + =item kill LIST Sends a signal to a list of processes. The first element of @@ -4475,8 +4483,11 @@ command if the files already exist: Returns a list consisting of all the values of the named hash. (In a scalar context, returns the number of values.) The values are -returned in an apparently random order, but it is the same order as -either the C<keys()> or C<each()> function would produce on the same hash. +returned in an apparently random order. The actual random order is +subject to change in future versions of perl, but it is guaranteed to +be the same order as either the C<keys()> or C<each()> function would +produce on the same (unmodified) hash. + As a side effect, it resets HASH's iterator. See also C<keys()>, C<each()>, and C<sort()>. diff --git a/pod/perlguts.pod b/pod/perlguts.pod index 7ccb80e15a..b835b59a38 100644 --- a/pod/perlguts.pod +++ b/pod/perlguts.pod @@ -350,11 +350,13 @@ This returns NULL if the variable does not exist. The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro: - i = klen; hash = 0; - s = key; - while (i--) - hash = hash * 33 + *s++; + while (klen--) + hash = (hash * 33) + *key++; + hash = hash + (hash >> 5); /* after 5.006 */ + +The last step was added in version 5.006 to improve distribution of +lower bits in the resulting hash value. See L<Understanding the Magic of Tied Hashes and Arrays> for more information on how to use the hash access functions on tied hashes. |