world.MtRand

MUSHclient script function (Method) — introduced in version 3.57

Returns pseudo-random number using the Mersenne Twister algorithm

Prototype

double MtRand();

Data type meanings

Description

This returns a pseudo-random number in the range 0 to 1 (however excluding 1) as a "double" (floating-point number). Thus you can generate a number in any range by multiplying the result by the range you want.

eg.

print (math.floor (MtRand () * 5)) - returns 0 to 4

See below in the Lua section for an example of doing coin flips.

Note that the MT generator is "global" to all of MUSHclient. If you are trying to reproduce a sequence, then you cannot rely on a sequence staying stable from one script call to another (since another script, or another world or plugin, might also use random numbers).

This (Lua) script here, for example, would generate a million random numbers, and put them into a table for later use:

nums = {} -- empty table

MtSrand (1234567) -- start with a known seed

for j = 1, 1000000 do
table.insert (nums, MtRand ())
end

This took about a second to execute on my PC.

Over a run of 10,000,000 coins flips it seemed pretty accurate, giving 5,000,625 heads and 4,999,375 tails (in other words, around 50.00625% heads).

Example (in Lua) of rolling a 6-sided die:

for i = 1, 100 do
Tell (math.floor (MtRand () * 6) + 1, " ")
end

In the above example, multiplying by 6 gives a number in the range 0 to 5, and then we add 1 to make it 1 to 6.

For more details about the Mersenne Twister see:

http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html

VBscript example

Note MtRand

Jscript example

Note (MtRand ())

Lua example

heads = 0
tails = 0

for j = 1, 1000000 do
  i = math.floor (MtRand () * 2)
  if i == 0 then
    heads = heads + 1
  else
    tails = tails + 1
  end  -- if
end  -- for

print ("heads = ", heads) --> 498893
print ("tails = ", tails) --> 501107

Return value

A pseudo-random number in the range [0 to 1). In other words, zero might be returned, however 1 will not be.

To put it another way, the returned number is:

>= 0 and < 1