zero

Given two floating-point numbers, I'm looking for an efficient way to check if they have the same sign, given that if any of the two values is zero (+0.0 or -0.0), they should be considered to have the same sign . For instance, SameSign(1.0, 2.0) should return true SameSign(-1.0, -2.0) should return true SameSign(-1.0, 2.0) should return false SameSign(0.0, 1.0) should return true SameSign(0.0, -1.0) should return true SameSign(-0.0, 1.0) should return true SameSign(-0.0, -1.0) should return true A naive but correct implementation of SameSign in C++ would be: bool SameSign(float a, float b) {

I want to pad some percentage values so that there are always 3 units before the decimal place. With ints I could use '%03d' - is there an equivalent for floats? '%.3f' works for after the decimal place but '%03f' does nothing. '%03.1f' works (1 could be any number, or empty string): >>> "%06.2f"%3.3 '003.30' >>> "%04.f"%3.2 '0003' Note that the field width includes the decimal and fractional digits. Alternatively, if you want to use .format : {:6.1f} ↑ ↑ | | # digits to pad | | # of decimal places to display Copypasta: {:6.1f} Example of usage: 'Num: {:6.1f}'.format(number) You could use

I would like to understand how to set 0 value of the attribute when it is NULL with MAX function. For example: Name columns: number - date Values: 10 - 2012-04-04 11 - 2012-04-04 12 - 2012-04-04 13 - 2012-04-15 14 - 2012-06-21 1 - 2013-07-04 Number is incremental field, but it has set itself 1 when new year has come. But result of: SELECT (MAX(number)+1) number WHERE date LIKE "2014%" is NULL and not 1 because MAX(number) is NULL and not 0 Well, as there is no date like 2014, you would expect null, because the maximum of nothing is actually not anyting. But do this: COALESCE(MAX(number),0)

Is it possible to check if a float is a positive zero (0.0) or a negative zero (-0.0)? I've converted the float to a String and checked if the first char is a '-' , but are there any other ways? Yes, divide by it. 1 / +0.0f is +Infinity , but 1 / -0.0f is -Infinity . It's easy to find out which one it is with a simple comparison, so you get: if (1 / x > 0) // +0 here else // -0 here (this assumes that x can only be one of the two zeroes) You can use Float.floatToIntBits to convert it to an int and look at the bit pattern: float f = -0.0f; if (Float.floatToIntBits(f) == 0x80000000) { System.out

I wonder, how can I create a numeric zero-length vector in R? If you read the help for vector (or numeric or logical or character or integer or double , 'raw' or complex etc ) then you will see that they all have a length (or length.out argument which defaults to 0 Therefore numeric() logical() character() integer() double() raw() complex() vector('numeric') vector('character') vector('integer') vector('double') vector('raw') vector('complex') All return 0 length vectors of the appropriate atomic modes. # the following will also return objects with length 0 list() expression() vector('list')

While looking through some c header files (specifically stdarg.h ), I noticed a very peculiar line: #if !defined(__STRICT_ANSI__) || __STDC_VERSION__ + 0 >= 199900L The strange part is the + 0 . Zero is the additive identity; it's one of the various math has of writing noop . What purpose does adding zero have in the above preprocessor statement? I know that there's all sorts of weird preprocessor magic out there, but this just seems ridiculous. That avoids a preprocessor syntax error if __STDC_VERSION__ is defined as an empty token (e.g. with #define __STDC_VERSION__ ). (Thanks to Jens