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Negative base numbers: Difference between revisions
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195 decoded in base -10 = 15
</pre>
=={{header|Ruby}}==
{{trans|Julia}}
{{works with|Ruby|2.3}}
<lang ruby>DIGITS = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
# convert a base 10 integer into a negative base value (as a string)
def negative_base_encode(n, b)
raise 'base out of range' if (b < -62) || (b > -2)
return '0' if n == 0
revdigs = []
while n != 0 do
n, r = n.divmod(b)
if r < 0
n += 1
r -= b
end
revdigs << r
end
return revdigs.reduce('') { |digstr, digit| DIGITS[digit] + digstr }
end
# convert a negative base value (as a string) into a base 10 integer
def negative_base_decode(n, b)
raise 'base out of range' if (b < -62) || (b > -2)
value = 0
n.reverse.each_char.with_index do |ch, inx|
value += DIGITS.index(ch) * b**inx
end
return value
end
# do the task
[ [10, -2], [146, -3], [15, -10], [0, -31], [-6221826, -62] ].each do |pair|
decimal, base = pair
encoded = negative_base_encode(decimal, base)
decoded = negative_base_decode(encoded, base)
puts("Enc: %8i base %-3i = %5s base %-3i Dec: %5s base %-3i = %8i base %-3i" %
[decimal, 10, encoded, base, encoded, base, decoded, 10])
end</lang>
{{out}}
<pre>Enc: 10 base 10 = 11110 base -2 Dec: 11110 base -2 = 10 base 10
Enc: 146 base 10 = 21102 base -3 Dec: 21102 base -3 = 146 base 10
Enc: 15 base 10 = 195 base -10 Dec: 195 base -10 = 15 base 10
Enc: 0 base 10 = 0 base -31 Dec: 0 base -31 = 0 base 10
Enc: -6221826 base 10 = Ruby base -62 Dec: Ruby base -62 = -6221826 base 10</pre>
=={{header|Rust}}==
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