double

问题 Im trying to change from big endian to little endian on a double. One way to go is to use double val, tmp = 5.55; ((unsigned int *)&val)[0] = ntohl(((unsigned int *)&tmp)[1]); ((unsigned int *)&val)[1] = ntohl(((unsigned int *)&tmp)[0]); But then I get a warning: "dereferencing type-punned pointer will break strict-aliasing rules" and I dont want to turn this warning off. Another way to go is: #define ntohll(x) ( ( (uint64_t)(ntohl( (uint32_t)((x << 32) >> 32) )) << 32) | ntohl( ((uint32_t)(x

问题 completed: React.PropTypes.number, Can i specify a minimum and maximum to a number props in React component. expected something like following: completed: React.PropTypes.numberBetween(min, max), I generate an array to specify the range attempt: completed: React.PropTypes.oneOf(Array.from({length: max -min+1, (v, k) => k + min})), However , i want completed props to accept also float as well , whereas , it accepts only integer now . How to make the following constraints combined : prop is

问题 If I perform 97346822*3f, result is 2.9204048E8, however 97346822*3.0 gives me 2.92040466E8. Please explain. 回答1: The number 3.0 is the literal representation of a double value (it's equivalent to 3.0d ), whereas 3.0f is a float value. The different precisions explain why you're getting different results - a double is stored using 64-bits, a float uses 32-bits. 回答2: 97346822*3.0 will be treated as double . Based on oracle tutorial The double data type is a double-precision 64-bit IEEE 754

问题 I have double (or float) variables that might be "empty", as in holding no valid value. How can I represent this condition with the built in types float and double? One option would be a wrapper that has a float and a boolean, but that can´t work, as my libraries have containers that store doubles and not objects that behave as doubles. Another would be using NaN (std::numeric_limits). But I see no way to check for a variable being NaN. How can I solve the problem of needing a "special" float

问题 I am trying to display numbers in a string dynamically, so if the number has decimal's display them but if not don"t show the .0 example: display 5.5 as 5.5 and 5.0 as 5 This is what I have so far: (answer is a double) double temp = answer; long temp2 = (long) temp; if (temp == temp2) { output = String.valueOf(temp2); System.out.println(output); this work's fine up to about 1e18 then will error out because of the maximum size of a Long. So how would I achieve this on bigger numbers like 5

问题 Consider the following snippet of code: float val1 = 214.20; double val2 = 214.20; printf("float : %f, %4.6f, %4.2f \n", val1, val1, val1); printf("double: %f, %4.6f, %4.2f \n", val2, val2, val2); Which outputs: float : 214.199997, 214.199997, 214.20 | <- the correct value I wanted double: 214.200000, 214.200000, 214.20 | I understand that 214.20 has an infinite binary representation. The first two elements of the first line have an approximation of the intended value, but the the last one

问题 The MySQL documentation for the DOUBLE type is really opaque as to what the minimum and maximum values are. Permissible values are -1.7976931348623157E+308 to -2.2250738585072014E-308, 0, and 2.2250738585072014E-308 to 1.7976931348623157E+308. This doesn't make sense to me. Maybe I'm being a mathtard, but I'm not understanding this. There appears to be two possible ranges and zero. 回答1: Yes, it has a range of possible positive values, zero, and a range of possible negative values. The reason

问题 The MySQL documentation for the DOUBLE type is really opaque as to what the minimum and maximum values are. Permissible values are -1.7976931348623157E+308 to -2.2250738585072014E-308, 0, and 2.2250738585072014E-308 to 1.7976931348623157E+308. This doesn't make sense to me. Maybe I'm being a mathtard, but I'm not understanding this. There appears to be two possible ranges and zero. 回答1: Yes, it has a range of possible positive values, zero, and a range of possible negative values. The reason

问题 This question already has answers here : What does ~~ (“double tilde”) do in Javascript? (9 answers) `Math.trunc` vs `|0` vs `<<0` vs `>>0` vs `&-1` vs `^0` (2 answers) Closed 5 years ago . I understand that ~ is a bitwise NOT operator, but how does inverting the bits on a number twice make it function as Math.floor What does ~~ ("double tilde") do in Javascript? describes the differences between using Math.floor vs bitwise operations to round numbers in Javascript, but I am interested in how

问题 This question already has answers here : What's the first double that deviates from its corresponding long by delta? (4 answers) Which is the first integer that an IEEE 754 float is incapable of representing exactly? (2 answers) Closed 6 years ago . What is the exact range of (contiguous) integers that can be expressed as a double (resp. float?) The reason I ask is because I am curious for questions such as this one when a loss of accuracy will occur. That is What is the least positive