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May
14
comment Single codebase for client and server with Node.js
@hippietrail, en.wikipedia.org/wiki/WAR_file_format_(Sun)
May
14
answered Single codebase for client and server with Node.js
May
4
comment Is there any situation when there's no alternative to instanceof?
There's a variant on the second approach which can be used in e.g. Java: try an explicit cast and be ready to catch the ClassCastException. It's probably open for debate whether this is really just hiding an instanceof check behind syntactic sugar.
May
1
awarded  Nice Answer
Apr
26
comment Why does Donald Knuth write TAOCP using assembly language?
Knuth implemented an ALGOL compiler in 1960, and ALGOL was intended to be suitable for publishing algorithms, so I don't think this really answers the question.
Apr
25
awarded  Custodian
Apr
17
comment Does any well-known license require to make modifications available when only derived *output* is published?
The GPL itself claims to be protected by copyright, so unless the lawyer / law student thinks they have a solid argument that it's ineligible, they might be reluctant to create an unauthorised derived work.
Apr
12
answered How can I evaluate a candidate's knowledge of Html/CSS during an interview?
Apr
5
comment Implementing base-10 floating point division
Your multiplication is a bit overkill. You're multiplying two 9-digit numbers, so the result will have 17 or 18 digits. You then want to reduce to 9 digits, so you're dropping 8 or 9 digits. Therefore you can safely drop the bottom 3 digits from each number before multiplying, and eliminate all of the terms containing C or F.
Apr
4
revised Computing integration with the Trapezoidal Rule
Fix scope
Apr
3
comment Is (1/(1/x)) always a perfect round trip?
Nice use of the pigeonhole principle. It can be extended to get a bound equal to my estimate for the number of collisions. For x in (1, 2), the range (x, 2) maps onto the range (0.5, x^-1), so given the difference in ulp the proportion of collisions is at least (2 - x) - 2(x^-1 - 0.5) = 3 - x - 2x^-1. Differentiate: this has extrema when -1 + 2x^-2 = 0 i.e. x^2 = 2. Only the positive root is in range, so we get that the proportion of collisions is at least 3 - sqrt(2) - 2/sqrt(2) = 3 - 2sqrt(2).
Apr
2
awarded  Nice Answer
Apr
2
revised Is (1/(1/x)) always a perfect round trip?
Analysis backs up empirical results
Apr
1
comment Is (1/(1/x)) always a perfect round trip?
@MichaelShaw, there's no good reason to expect that the reciprocal should even be injective, which would be a precondition for double-reciprocal to round-trip. However, there's a difference between a) stating without proof that there's probably at least one number that doesn't round-trip; b) calculating and justifying an estimate for the number of mantissas which don't round-trip; c) proving that at least one mantissa doesn't round-trip. I would be quite interested to see a careful analysis which shows how good or bad my empirical measurement is.
Apr
1
comment Is (1/(1/x)) always a perfect round trip?
Empirically your rule of thumb is wrong: it returns true for slightly over 80% of values of x.
Apr
1
answered Is (1/(1/x)) always a perfect round trip?
Apr
1
comment Is (1/(1/x)) always a perfect round trip?
You cannot conclude from the fact that 1/x can't be represented exactly that 1/(1/x) != x. To take your example, in 3.s.f. decimal floating point, 1.00 / 3.00 = 0.333, and 1.00 / 0.333 is 3.00. That particular mantissa is a fixed point of the double-reciprocal in that floating point scheme.
Mar
21
comment Why interviewers want Optimal Algorithms
Are you sure they were doubtful about the correctness and not just wanting to see how clearly you were capable of explaining its working?
Mar
20
comment Login on every page requires SSL on all pages
FWIW some XSS vectors would allow the attacker to send information to an attacker-controlled site even if the page with the login form is only sent over HTTPS.
Feb
27
comment Validating Emails in PHP
@AmgadSuliman, probably not, but if you download IsEmail you can use its test suite to check most if not all of the corner cases.