? Roll - Deal

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Roll | ? ?. 0 0 0 | Deal

`? y` yields a uniform random selection from the population`i.y` if`y` is a positive integer, or from the interval of numbers greater than or equal to 0 and less than 1, if`y` is 0.`` The random seed used begins at`7^5` (16807). |  | `x ? y` is a list of`x` items randomly chosen without repetition from`i.y` .

The corresponding use of`?.` proceeds from a fixed random seed of`7^5` and has no effect on the results of`?` (monad or dyad). Use of the fixed seed function`?.` makes examples reproducible:

       ?. 6
    0

       ?. 6 6 6 6 6 6 6 6
    0 5 5 4 2 3 2 1

       6 ?. 6                     A random permutation
    0 1 5 4 3 2

       mean=: +/ % #
       mean ?. 1000 # 6
    2.459

       ] m=: ?. 4 4 $ 9           A random matrix for experimentation
    3 8 8 4
    2 0 2 7
    4 2 3 5
    1 1 7 2

       -/ . * m                   The determinant of m
    _659

       f=: ?.@$ % ] - 1:
       3 6 f 9                    Random 3 by 6 table in range zero to one with resolution 9
    0.375     1     1  0.5  0.25     0
     0.25 0.875   0.5 0.25 0.375 0.625
    0.125 0.125 0.875 0.25 0.875  0.75

The random seed (a beginning value for the pseudo-random number generator) is set by the foreign conjunction using`9!:1`,`` and queried with`9!:0` . The algorithm is`GB_Flip` (Knuth [15]) with a period length of at least`_1+2^55` .

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