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| author | Roberto Ierusalimschy <roberto@inf.puc-rio.br> | 2019-03-13 14:47:48 -0300 |
|---|---|---|
| committer | Roberto Ierusalimschy <roberto@inf.puc-rio.br> | 2019-03-13 14:47:48 -0300 |
| commit | 9eca305e75010e30342486a4139846faf1b3eccb (patch) | |
| tree | db2df6774e7c4eb63d2310772507c47e32223cdd /manual | |
| parent | c5feac2b5edf86aa9bdc4b8acd5380f2fe9e197f (diff) | |
| download | lua-9eca305e75010e30342486a4139846faf1b3eccb.tar.gz lua-9eca305e75010e30342486a4139846faf1b3eccb.tar.bz2 lua-9eca305e75010e30342486a4139846faf1b3eccb.zip | |
'math.randomseed()' sets a somewhat random seed
When called with no arguments, 'math.randomseed' uses time and ASLR
to generate a somewhat random seed. the initial seed when Lua starts
is generated this way.
Diffstat (limited to 'manual')
| -rw-r--r-- | manual/manual.of | 23 |
1 files changed, 14 insertions, 9 deletions
diff --git a/manual/manual.of b/manual/manual.of index 2eb8773f..b47fd865 100644 --- a/manual/manual.of +++ b/manual/manual.of | |||
| @@ -7643,14 +7643,10 @@ is equivalent to @T{math.random(1,n)}. | |||
| 7643 | The call @T{math.random(0)} produces an integer with | 7643 | The call @T{math.random(0)} produces an integer with |
| 7644 | all bits (pseudo)random. | 7644 | all bits (pseudo)random. |
| 7645 | 7645 | ||
| 7646 | Lua initializes its pseudo-random generator with | 7646 | Lua initializes its pseudo-random generator with the equivalent of |
| 7647 | a weak attempt for ``randomness'', | 7647 | a call to @Lid{math.randomseed} with no arguments, |
| 7648 | so that @id{math.random} should generate | 7648 | so that @id{math.random} should generate |
| 7649 | different sequences of results each time the program runs. | 7649 | different sequences of results each time the program runs. |
| 7650 | To ensure a required level of randomness to the initial state | ||
| 7651 | (or contrarily, to have a deterministic sequence, | ||
| 7652 | for instance when debugging a program), | ||
| 7653 | you should call @Lid{math.randomseed} explicitly. | ||
| 7654 | 7650 | ||
| 7655 | The results from this function have good statistical qualities, | 7651 | The results from this function have good statistical qualities, |
| 7656 | but they are not cryptographically secure. | 7652 | but they are not cryptographically secure. |
| @@ -7660,14 +7656,23 @@ some number of previous results.) | |||
| 7660 | 7656 | ||
| 7661 | } | 7657 | } |
| 7662 | 7658 | ||
| 7663 | @LibEntry{math.randomseed (x [, y])| | 7659 | @LibEntry{math.randomseed ([x [, y]])| |
| 7664 | 7660 | ||
| 7665 | The integer parameters @id{x} and @id{y} are | 7661 | When called with at least one argument, |
| 7666 | concatenated into a 128-bit @Q{seed} that | 7662 | the integer parameters @id{x} and @id{y} are |
| 7663 | concatenated into a 128-bit @emphx{seed} that | ||
| 7667 | is used to reinitialize the pseudo-random generator; | 7664 | is used to reinitialize the pseudo-random generator; |
| 7668 | equal seeds produce equal sequences of numbers. | 7665 | equal seeds produce equal sequences of numbers. |
| 7669 | The default for @id{y} is zero. | 7666 | The default for @id{y} is zero. |
| 7670 | 7667 | ||
| 7668 | When called with no arguments, | ||
| 7669 | Lua generates a seed with | ||
| 7670 | a weak attempt for randomness. | ||
| 7671 | To ensure a required level of randomness to the initial state | ||
| 7672 | (or contrarily, to have a deterministic sequence, | ||
| 7673 | for instance when debugging a program), | ||
| 7674 | you should call @Lid{math.randomseed} with explicit arguments. | ||
| 7675 | |||
| 7671 | } | 7676 | } |
| 7672 | 7677 | ||
| 7673 | @LibEntry{math.sin (x)| | 7678 | @LibEntry{math.sin (x)| |