diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 27 |
1 files changed, 24 insertions, 3 deletions
@@ -12546,7 +12546,7 @@ the call (make-random-state 42). .TP Syntax: - (make-random-state <seed>) + (make-random-state [<seed>]) .TP Description: @@ -12554,11 +12554,32 @@ Description: The make-random-state function creates and returns a new random state, an object of the same kind as what is stored in the *random-state* variable. -The seed must be an integer value. +The seed, if specified, must be an integer value. -Note that the sign of the value is ignored, so that negative seed +Note that the sign of the seed is ignored, so that negative seed values are equivalent to their additive inverses. +If the seed is not specified, then make-random-state produces a seed based +on some information in the process environment, such as current +time of day. It is not guaranteed that two calls to (make-random-state nil) +that are separated by less than some minimum increment of real time produce +different seeds. The minimum time increment depends on the platform, but on any +given platform, it is the platform's smallest available time increment, or a +microsecond, whichever is longer. + +Of course, it is not guranteed that any two calls to make-random-state produce +different values under any circumstances, due to possible collisions; however, +time differences smaller than the minimum increment may predictably produce +identical values. + +For instance, on a platform with a nanosecond-resolution real-time clock, +the minimum time increment is a microsecond. Calls to make-random-state +closer together than a microsecond may predictably produce the same seed. + +In a platform with a millisecond-resolution real-time clock, the minimum +time increment is a millisecond. Calls to make-random-state less than +a millisecond apart may predictably produce the same seed. + .SS Function random-state-p .TP |