modulo

Is there a built in function that would allow me to calculate the modular inverse of a(mod n)? e.g. 19^-1 = 11 (mod 30), in this case the 19^-1 == -11==19; Anton Samsonov Since .Net 4.0+ implements BigInteger with a special modular arithmetics function ModPow (which produces “ X power Y modulo Z ”), you don't need a third-party library to emulate ModInverse. If n is a prime, all you need to do is to compute: a_inverse = BigInteger.ModPow(a, n - 2, n) For more details, look in Wikipedia: Modular multiplicative inverse , section Using Euler's theorem , the special case “when m is a prime” . By

In Python and Ruby, signed integer division truncates towards negative infinity, and signed integer modulus has the same sign the second operand: >>> (-41) / 3 -14 >>> (-41) % 3 1 However, in C and Java, signed integer division truncates towards 0, and signed integer modulus has the same sign as the first operand: printf("%d\n", (-41) / 3); /* prints "-13" */ printf("%d\n", (-41) % 3); /* prints "-2" */ What is the simplest and most efficient way in C to perform the same kind of division and modulus as in Python and Ruby? Ville Laurikari The direction for rounding with signed integer division

Is it guaranteed that (-x) % m , where x and m are positive in c++ standard (c++0x) is negative and equals to -(x % m) ? I know it's right on all machines I know. In addition to Luchian 's answer, this is the corresponding part from the C++11 standard: The binary / operator yields the quotient, and the binary % operator yields the remainder from the division of the first expression by the second. If the second operand of / or % is zero the behavior is undefined. For integral operands the / operator yields the algebraic quotient with any fractional part discarded; if the quotient a/b is

Questions arise when I type in these expressions to Python 3.3.0 -10 // 3 # -4 -10 % 3 # 2 10 // -3 # -4 10 % -3 # -2 -10 // -3 # 3 It appears as though it takes the approximate floating point (-3.33)? and rounds down either way in integer division but in the modulo operation it does something totally different. It seems like it returns the remainder +/-1 and only switches the sign depending on where the negative operand is. I am utterly confused, even after looking over other answers on this site! I hope someone can clearly explain this too me! The book says hint: recall this magic formula a

Note: This is a self Q&A When building asymmetrical grid layouts in WordPress, it's common that you'd want to wrap each X post in a div, like so: div post post /div div post post /div div post post /div I'd like to avoid using a modulo operator as it gets confusing quickly. Drew Baker Most people do this with a modulo operator, but it gets awkward to do it if no posts are found, or and even division occurs on the last post. I've expanded on the answer provided here by @The Shift Exchange to do it in a cleaner way. <?php // Get posts (tweak args as needed) $args = array( 'post_type' => 'page',

What exactly does this mean? $number = ( 3 - 2 + 7 ) % 7; It's the modulus operator, as mentioned, which returns the remainder of a division operation. Examples: 3%5 returns 3, as 3 divided by 5 is 0 with a remainder of 3. 5 % 10 returns 5, for the same reason, 10 goes into 5 zero times with a remainder of 5. 10 % 5 returns 0, as 10 divided by 5 goes exactly 2 times with no remainder. In the example you posted, (3 - 2 + 7) works out to 8, giving you 8 % 7 , so $number will be 1 , which is the remainder of 8/7. Pascal MARTIN It is the modulus operator : $a % $b = Remainder of $a divided by $b .