blocks|key|1628505|text|在拼音中，Fixnums会自动转换为Bignums。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1628506|要找到尽可能高的Fixnum，您可以这样做：|1628507|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)|code-block|syntax|javascript|1628508|厚颜无耻地从ruby-talk+discussion上扯下来。请查看此处了解更多详细信息。|offset|length|1628509|entityMap|0|LINK|mutability|MUTABLE|url|http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/149748^0|0|0|0|6|K|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@$K|Y|L|Z|1|10]]|A|$]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

In ruby Fixnums are automatically converted to Bignums.

To find the highest possible Fixnum you could do something like this:

<pre><code>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)
</code></pre>

Shamelessly ripped from a <a href="http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/149748" rel="noreferrer">ruby-talk discussion</a>. Look there for more details.

blocks|key|1628523|text|阅读友好手册？谁会想这么做呢？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1628524|start+=+Time.now
largest_known_fixnum+=+1
smallest_known_bignum+=+nil

until+smallest_known_bignum+==+largest_known_fixnum+%2B+1
++if+smallest_known_bignum.nil?
++++next_number_to_try+=+largest_known_fixnum+*+1000
++else
++++next_number_to_try+=+(smallest_known_bignum+%2B+largest_known_fixnum)+/+2+#+Geometric+mean+would+be+more+efficient,+but+more+risky
++end

++if+next_number_to_try+<=+largest_known_fixnum+%7C%7C
+++++++smallest_known_bignum+&&+next_number_to_try+>=+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"|code-block|syntax|javascript|1628525|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Reading the friendly manual? Who'd want to do that?

<pre><code>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"
</code></pre>

blocks|key|1628545|text|FIXNUM_MAX+=+(2**(0.size+*+8+-2)+-1)
FIXNUM_MIN+=+-(2**(0.size+*+8+-2))|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1628546|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>FIXNUM_MAX = (2**(0.size * 8 -2) -1)
FIXNUM_MIN = -(2**(0.size * 8 -2))
</code></pre>

blocks|key|1628620|text|正如@Jörg+W+Mittag指出的:在jruby中，fix+num大小总是8字节长。下面的代码片段显示了事实：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1628621|fmax+=+->{
++if+RUBY_PLATFORM+==+'java'
++++2**63+-+1
++else
++++2**(0.size+*+8+-+2)+-+1
++end
}.call

p+fmax.class+++++#+Fixnum

fmax+=+fmax+%2B+1++

p+fmax.class+++++#Bignum|code-block|syntax|javascript|1628622|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

as @Jörg W Mittag pointed out: in jruby, fix num size is always 8 bytes long. This code snippet shows the truth:

<pre><code>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
</code></pre>

blocks|key|1628659|text|从Ruby+2.4开始没有最大值，因为Bignum和Fixnum统一为Integer。请参阅Feature+#12005|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1628660|>+(2+<<+1000).is_a?+Fixnum
(irb):322:+warning:+constant+::Fixnum+is+deprecated
=>+true

>+1.is_a?+Bignum
(irb):314:+warning:+constant+::Bignum+is+deprecated
=>+true

>+(2+<<+1000).class
=>+Integer|code-block|syntax|javascript|1628661|不会有任何溢出，发生的是内存不足。|1628662|entityMap|0|LINK|mutability|MUTABLE|url|https://bugs.ruby-lang.org/issues/12005^0|1A|E|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

There is no maximum since Ruby 2.4, as Bignum and Fixnum got unified into Integer. see <a href="https://bugs.ruby-lang.org/issues/12005" rel="nofollow noreferrer">Feature #12005</a>

<pre class="lang-rb prettyprint-override"><code>&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
</code></pre>

There won't be any overflow, what would happen is an out of memory.

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

Ruby max integer

我需要能够在Ruby中确定系统的最大整数。有人知道是怎么回事吗，或者有没有可能？

问Ruby最大整数
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