Ruby max integer

Question

I need to be able to determine a systems maximum integer in Ruby  Anybody know how  or if it s possible

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as  J  rg W Mittag pointed out  in jruby  fix num size is always 8 bytes long  This code snippet shows the truth   fmax   - gt     if RUBY PLATFORM     java      2  63 - 1   else     2   0 size   8 - 2  - 1   end   call  p fmax class       Fixnum  fmax   fmax   1    p fmax class      Bignum

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Reading the friendly manual  Who d want to do that   start   Time now largest known fixnum   1 smallest known bignum   nil  until smallest known bignum    largest known fixnum   1   if smallest known bignum nil      next number to try   largest known fixnum   1000   else     next number to try    smallest known bignum   largest known fixnum    2   Geometric mean would be more efficient  but more risky   end    if next number to try  lt   largest known fixnum           smallest known bignum  amp  amp  next number to try  gt   smallest known bignum     raise  Can t happen case     end    case next number to try     when Bignum then smallest known bignum   next number to try     when Fixnum then largest known fixnum   next number to try     else raise  Can t happen case    end end  finish   Time now puts  The largest fixnum is   largest known fixnum   puts  The smallest bignum is   smallest known bignum   puts  Calculation took   finish - start  seconds

User · Answer

In ruby Fixnums are automatically converted to Bignums   To find the highest possible Fixnum you could do something like this   class Fixnum  N BYTES    42  pack  i   size  N BITS   N BYTES   8  MAX   2     N BITS - 2  - 1  MIN   -MAX - 1 end p Fixnum  MAX    Shamelessly ripped from a ruby-talk discussion   Look there for more details

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Ruby automatically converts integers to a large integer class when they overflow  so there s  practically  no limit to how big they can be   If you are looking for the machine s size  i e  64- or 32-bit  I found this trick at ruby-forum com   machine bytes     foo   pack  p   size machine bits   machine bytes   8 machine max signed   2   machine bits-1  - 1 machine max unsigned   2  machine bits - 1     If you are looking for the size of Fixnum objects  integers small enough to store in a single machine word   you can call 0 size to get the number of bytes  I would guess it should be 4 on 32-bit builds  but I can t test that right now  Also  the largest Fixnum is apparently 2  30 - 1  or 2  62 - 1   because one bit is used to mark it as an integer instead of an object reference

User · Answer

FIXNUM MAX    2   0 size   8 -2  -1  FIXNUM MIN   - 2   0 size   8 -2

User · Answer

There is no maximum since Ruby 2 4  as Bignum and Fixnum got unified into Integer  see Feature  12005   gt   2  lt  lt  1000  is a  Fixnum  irb  322  warning  constant   Fixnum is deprecated   gt  true   gt  1 is a  Bignum  irb  314  warning  constant   Bignum is deprecated   gt  true   gt   2  lt  lt  1000  class   gt  Integer   There won t be any overflow  what would happen is an out of memory

[ruby] Ruby max integer

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