floating-point-conversion

问题 This question already has answers here : C program to convert Fahrenheit to Celsius always prints zero (8 answers) Why does division result in zero instead of a decimal? (5 answers) Closed last year . I am trying to calculate p1=(1/1)*(1/2)*...*(1/n) but something is wrong and the printf gives me 0.000...0 #include <stdio.h> int main(void) { int i,num; float p3; do { printf ("give number N>3 : \n" ); scanf( "%d", &num ); } while( num <= 3 ); i = 1; p3 = 1; do { p3=p3*(1/i); printf( "%f\n",p3

问题 So in JavaScript, 111111111111111111111 == 111111111111111110000. Just type any long number – at least about 17 digits – to see it in action ;-) That is because JavaScript uses double-precision floating-point numbers, and certain very long numeric literals can not be expressed accurately. Instead, those numbers get rounded to the nearest representable number possible. See e.g. What is JavaScript's highest integer value that a Number can go to without losing precision? However, doing the math

问题 While I'm using %g as format specifier in printf() , sometimes it rounds up upto 2 places after decimal point, sometimes upto 3 places , someimes upto 4 places...how it does so? Actually where we should use %g instead of %f or %e for floating point numbers? 回答1: The %g format specifier does its rounding just like %f would do, but if %f would result in 4.234000 , then %g will omit the trailing zeros and print 4.234 . %g should be used when it makes the most sense in your output format that

问题 So I have a file that has multiple strings. I'm supposed to use fgets to read each line then use sscanf to break the string up and process them into my struct. Here's an example. 38L Lee, Victor; 2.8 The first is the id, second is name, and finally the gpa. When I try using sscanf to read the gpa, it's reading 0.0, rather than 2.8. Here's my code. bool getstu (FILE* fpstu, STU* pstu) { // Local Definitions int ioResult; char temp[100]; char *ptr; char tempStr[50]; // Statements fgets(temp,

问题 I'm trying to send a 32-Bit Real across a CAN communications (IFM) but the CAN comms only accepts a 16-Bit value. If the value I'm trying to send goes above 255, it resets back to 0 and continues in that pattern. I therefore need to split the 32-Bit Real value in to two 16-Bit values and then reassemble on the other side of the comms. I just can't seem to get my head around how to do it in structured text. Any help would be appreciated 回答1: I know I am a little late to the party but wanted to

问题 For a project I need to read in information from MQTT. The payload is filled with protobuf information, that needs to be converted. For a certain value I receive 5.6904566139035E-28 as float. Using http://www.exploringbinary.com/floating-point-converter/ I can convert this when I tick single and raw hexadecimal value, then I receive 12345678, the value I should have (I know what is sent). But now I need to do that conversion in PHP. I haven't any idea how this could be done. After some

问题 This question already has answers here : strange output in comparison of float with float literal (8 answers) Closed 4 years ago . I was reading this. It contains following C program. #include<stdio.h> int main() { float x = 0.1; if (x == 0.1) printf("IF"); else if (x == 0.1f) printf("ELSE IF"); else printf("ELSE"); } The article says that The output of above program is “ELSE IF” which means the expression “x == 0.1″ returns false and expression “x == 0.1f” returns true. But I tried it on

问题 So I was trying to understand JavaScript's behavior when dealing with large numbers. Consider the following (tested in Firefox and Chrome): console.log(9007199254740993) // 9007199254740992 console.log(9007199254740994) // 9007199254740994 console.log(9007199254740995) // 9007199254740996 console.log(9007199254740996) // 9007199254740996 console.log(9007199254740997) // 9007199254740996 console.log(9007199254740998) // 9007199254740998 console.log(9007199254740999) // 9007199254741000 Now, I

问题 If I have a C# float , can I convert it to double without losing any precision? If that double were converted back to float , would it have exactly the same value? 回答1: Yes. IEEE754 floating point (which is what C# must use) guarantees this: Converting a float to a double preserves exactly the same value Converting that double back to a float recovers exactly that original float . The set of double s is a superset of float s. Note that this also applies to NaN , +Infinity , and -Infinity .

问题 This question has been asked a couple of times, but all the answers either refer to sprintf or involve deleting the trailing zeroes manually. Is there really no better way? is it not possible to achieve this with std::stringstream ? 回答1: First you calculate how many potential digits you have before and after the decimal: int digits_before = 1 + (int)floor(log10(fabs(value))); int digits_after = std::numeric_limits<double>::digits10 - digits_before; Then you find out how many of those digits