File : randdist.sp
$ spar randdist
aleph 2.00260000000000E-01 2.00000000000000E-01
beth 1.66376000000000E-01 1.66666666666667E-01
gimel 1.42698000000000E-01 1.42857142857143E-01
daleth 1.25408000000000E-01 1.25000000000000E-01
he 1.11311000000000E-01 1.11111111111111E-01
waw 9.97980000000000E-02 1.00000000000000E-01
zayin 9.09570000000000E-02 9.09090909090909E-02
heth 6.31920000000000E-02 rest
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#!/usr/local/bin/spar
pragma annotate( summary, "randdist" )
@( description, "Given a mapping between items and their required" )
@( description, "probability of occurrence, generate a million items" )
@( description, "randomly subject to the given probabilities and compare" )
@( description, "the target probability of occurrence versus the" )
@( description, "generated values." )
@( description, "" )
@( description, "The total of all the probabilities should equal one." )
@( description, "(Because floating point arithmetic is involved this is" )
@( description, "subject to rounding errors). Use the following mapping" )
@( description, "to test your programs: aleph 1/5.0, beth 1/6.0," )
@( description, "gimel 1/7.0, daleth 1/8.0, he 1/9.0, waw 1/10.0" )
@( description, "zayin 1/11.0, heth 1759/27720 adjusted so that" )
@( description, "probabilities add to 1" )
@( see_also, "http://rosettacode.org/wiki/Probabilistic_choice" )
@( author, "Ken O. Burtch" );
pragma license( unrestricted );
pragma restriction( no_external_commands );
procedure randdist is
trials : constant positive := 1_000_000;
type outcome is (aleph, beth, gimel, daleth, he, waw, zayin, heth);
pr : constant array(aleph..heth) of float :=
(1/5, 1/6, 1/7, 1/8, 1/9, 1/10, 1/11, 1 );
samples : array(aleph..heth) of natural := (0, 0, 0, 0, 0, 0, 0, 0);
random_value : float;
begin
for try in 1..trials loop
random_value := numerics.random;
for i in arrays.first( pr )..arrays.last( pr ) loop
if random_value <= pr(i) then
samples(i) := samples(i) + 1;
exit;
else
random_value := @ - pr(i);
end if;
end loop;
end loop;
-- Show results
for i in arrays.first( pr )..arrays.last( pr ) loop
put( i ) @ ( " " ) @ ( float( samples( i ) ) / float( trials ) );
if i = heth then
put_line( " rest" );
else
put_line( pr(i) );
end if;
end loop;
end randdist;
-- VIM editor formatting instructions
-- vim: ft=spar