The current answers all focus on decimal digits, when applying the “add all digits and see if that divides by 3”. That trick actually works in hex as well; e.g. 0x12 can be divided by 3 because 0x1 + 0x2 = 0x3. And “converting” to hex is a lot easier than converting to decimal. Pseudo-code: … Read more
The scanf call uses the wrong format string. You are reading an int so you need it to be: scanf(“%d”, &fahrenheit); The expression 5/9 is evaluated using integer division. In fact the compiler can work it out at compile time. That expression evaluates to 0. You need to perform floating point division. For instance: 5.0/9 … Read more
If the divisor is a signed 64-bit value, you don’t need to do anything with it. Likewise, if the dividend is a signed 128-bit value, you don’t need to do anything with it, just load the top 64 bits of it into rdx and the low 64 bits into rax. Now, if any of the … Read more
If you are storing the value (128-bits) using the largest possible native representation your architecture can handle (64-bits) you will have problems handling the intermediate results of the division (as you already found 🙂 ). But you always can use a SMALLER representation. What about FOUR numbers of 32-bits? This way you could use the … Read more
I’ll use uint64_t here (which needs the <stdint.h> include) so as not to require your assumption about the size of unsigned long. phuclv’s idea of using -n is clever, but can be made much simpler. As unsigned 64-bit integers, we have -n = 264-n, then (-n)/n = 264/n – 1, and we can simply add … Read more
After that, however, it subtracted (dividend/2^31) from the result. Actually, it subtracts dividend >> 31, which is -1 for negative dividend, and 0 for non-negative dividend, when right-shifting negative integers is arithmetic right-shift (and int is 32 bits wide). 0x6666667 = (2^34 + 6)/10 So for x < 0, we have, writing x = 10*k … Read more
Do floating point division then convert to an int. No extra modules needed. Python 3: >>> int(-1 / 2) 0 >>> int(-3 / 2) -1 >>> int(1 / 2) 0 >>> int(3 / 2) 1 Python 2: >>> int(float(-1) / 2) 0 >>> int(float(-3) / 2) -1 >>> int(float(1) / 2) 0 >>> int(float(3) / … Read more
The operands of the binary operation 3 / 10 are untyped constants. The specification says this about binary operations with untyped constants if the operands of a binary operation are different kinds of untyped constants, the operation and, for non-boolean operations, the result use the kind that appears later in this list: integer, rune, floating-point, … Read more
It’s because you’re doing integer division. Divide by a double or a float, and it will work: double scale = ( n / 1024.0 ) * 255 ; Or, if you want it as a float, float scale = ( n / 1024.0f ) * 255 ;
Cast one of the integers to float to ensure a floating point division: float result = integer1 / (float) integer2