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StackOverflow程序员推荐：每个程序员都应读的30本书 - 杂谈 - 清泛网 - 专...
...但我还是一定推荐给初学者。毕竟这本书是写给著名的6.001，是麻省理工学院的入门编程课程。此书或许需要多做努力（尤其你在做练习的时候，你也应当如此），但这个价是对得起这本书的。
你还不确信么？那就读读第一版...
Format an Integer using Java String Format
...
String.format("%03d", 1) // => "001"
// │││ └── print the number one
// ││└────── ... as a decimal integer
// │└─────── ... minimum of 3 characters wide
// ...
How to define custom configuration variables in rails
...HENTICATION constant everywhere in your application:
#rails c production
:001> AUTHENTICATION['username'] => 'aa'
then add passwords.yml to .gitignore: echo /config/passwords.yml >> .gitignore, create an example file for your comfort cp /config/passwords.yml /config/passwords.example.y...
Compare double to zero using epsilon
... greater than 1:
1.0000 00000000 00000000 00000000 00000000 00000000 00000001 × 2^0 = 1 + 2^-52
Therefore:
epsilon = (1 + 2^-52) - 1 = 2^-52
Are there any numbers between 0 and epsilon? Plenty... E.g. the minimal positive representable (normal) number is:
1.0000 00000000 00000000 00000000 00...
Truncate Two decimal places without rounding
....AreEqual(-1.12m, -1.1254m.TruncateEx(2));
Assert.AreEqual(0m, 0.0001m.TruncateEx(3));
Assert.AreEqual(0m, -0.0001m.TruncateEx(3));
Assert.AreEqual(0m, -0.0000m.TruncateEx(3));
Assert.AreEqual(0m, 0.0000m.TruncateEx(3));
Assert.AreEqual(1.1m, 1.12m. Truncate...
Formatting floats without trailing zeros
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The only problem with that is '%.2f' % -0.0001 will leave you with -0.00 and ultimately -0.
– Kos
Dec 7 '12 at 13:14
3
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What does “|=” mean? (pipe equal operator)
...OR to add flags
int myFlags = DEFAULT_SOUND | DEFAULT_VIBRATE; // same as 001 | 010, producing 011
so
myFlags |= DEFAULT_LIGHTS;
simply means we add a flag.
And symmetrically, we test a flag is set using & :
boolean hasVibrate = (DEFAULT_VIBRATE & myFlags) != 0;
...
Ruby Arrays: select(), collect(), and map()
...ct here, but the block is given the key and value in this case:
irb(main):001:0> h = {:sku=>"507772-B21", :desc=>"HP 1TB 3G SATA 7.2K RPM LFF (3 .", :qty=>"", :qty2=>"1", :price=>"5,204.34 P"}
irb(main):002:0> h.select { |key, value| !value.empty? }
=> {:sku=>"507772-B21"...
How to generate a git patch for a specific commit?
...
Adam Liss
44.1k1111 gold badges100100 silver badges140140 bronze badges
answered Jul 12 '11 at 0:43
manojldsmanojlds
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How to get execution time in rails console?
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With benchmark-ips gem:
2.3.0 :001 > require 'benchmark/ips'
=> true
2.3.0 :002 > Benchmark.ips do |x|
2.3.0 :003 > x.report("add: ") { 1+2 }
2.3.0 :004?> x.report("div: ") { 1/2 }
2.3.0 :005?> x.report("iis: ") { 1/2.0...