Benford's law: Difference between revisions
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</pre>
=={{header|BCPL}}==
BCPL doesn't do floating point well, so I use integer math to compute the most significant digits of the Fibonacci sequence and use a table that has the values of log10(d + 1/d)
<lang BCPL>
GET "libhdr"
MANIFEST {
fib_sz = 1_000_000_000 // keep 9 significant digits for computing F(n)
}
LET msd(n) = VALOF {
UNTIL n < 10 DO
n /:= 10
RESULTIS n
}
LET fibonacci(n, tally) BE {
LET a, b, c, e = 0, 1, ?, 0
FOR i = 1 TO n {
TEST e = 0
THEN tally[msd(b)] +:= 1
ELSE tally[b / (fib_sz / 10)] +:= 1
c := a + b
IF c > fib_sz {
a := a / 10 - (a MOD 10 >= 5) // subtract, since condition evalutes to
b := b / 10 - (b MOD 10 >= 5) // eithr 0 or -1.
c := a + b
e +:= 1 // keep track of exponent, just 'cuz
}
a, b := b, c
}
}
LET start() = VALOF {
// expected value of benford: log10(d + 1/d)
LET expected = TABLE 0, 301, 176, 125, 97, 79, 67, 58, 51, 46
LET actual = VEC 9
FOR i = 0 TO 9 DO actual!i := 0
fibonacci(1000, actual)
writes("*nLeading digital distribution of the first 1,000 Fibonacci numbers*n")
writes("Digit*tActual*tExpected*n")
FOR i = 1 TO 9
writef("%i *t%0.3d *t%0.3d *n", i, actual!i, expected!i)
RESULTIS 0
}
</lang>
{{Out}}
<pre>
BCPL 64-bit Cintcode System (13 Jan 2020)
0.000>
Leading digital distribution of the first 1,000 Fibonacci numbers
Digit Actual Expected
1 0.301 0.301
2 0.177 0.176
3 0.125 0.125
4 0.096 0.097
5 0.080 0.079
6 0.067 0.067
7 0.056 0.058
8 0.053 0.051
9 0.045 0.046
</pre>
=={{header|C}}==
<lang c>#include <stdio.h>
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