How do I determine the length of a Fixnum in Ruby?
puts Math.log10(1234).to_i + 1 # => 4
You could add it to Fixnum like this:
class Fixnum
def num_digits
Math.log10(self).to_i + 1
end
end
puts 1234.num_digits # => 4
Ruby 2.4 has an Integer#digits method, which return an Array containing the digits.
num = 123456
num.digits
# => [6, 5, 4, 3, 2, 1]
num.digits.count
# => 6
EDIT:
To handle negative numbers (thanks @MatzFan), use the absolute value. Integer#abs
-123456.abs.digits
# => [6, 5, 4, 3, 2, 1]
Sidenote for Ruby 2.4+
I ran some benchmarks on the different solutions, and Math.log10(x).to_i + 1
is actually a lot faster than x.to_s.length
. The comment from @Wayne Conrad is out of date. The new solution with digits.count
is trailing far behind, especially with larger numbers:
with_10_digits = 2_040_240_420
print Benchmark.measure { 1_000_000.times { Math.log10(with_10_digits).to_i + 1 } }
# => 0.100000 0.000000 0.100000 ( 0.109846)
print Benchmark.measure { 1_000_000.times { with_10_digits.to_s.length } }
# => 0.360000 0.000000 0.360000 ( 0.362604)
print Benchmark.measure { 1_000_000.times { with_10_digits.digits.count } }
# => 0.690000 0.020000 0.710000 ( 0.717554)
with_42_digits = 750_325_442_042_020_572_057_420_745_037_450_237_570_322
print Benchmark.measure { 1_000_000.times { Math.log10(with_42_digits).to_i + 1 } }
# => 0.140000 0.000000 0.140000 ( 0.142757)
print Benchmark.measure { 1_000_000.times { with_42_digits.to_s.length } }
# => 1.180000 0.000000 1.180000 ( 1.186603)
print Benchmark.measure { 1_000_000.times { with_42_digits.digits.count } }
# => 8.480000 0.040000 8.520000 ( 8.577174)