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Zufolek on 11/24/09

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# Some handy math functions

/ Published in: C   Functions for generating random numbers, flipping coins, rolling dice, etc.

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`#include <stdio.h>#include <stdlib.h>#include <math.h>#include <assert.h>  //define NDEBUG if you want to remove asserts  //the following function//returns a random non-negative integer less than h//h must obviously be less than or equal to the highest number//possible from the random number generator int rnd(int h){ if(!h)return 0;//making sure we don't divide by zero! assert(h<=RAND_MAX); return rand()%h;}  //rolls a virtual die//(die is the singular of dice)//returns a number 1-6 int rolldie(){ return rnd(6)+1;}  //flips a virtual coin//returns 1 or 0 for heads or tails int flipcoin(){ return rand()&1;}   //returns a floating point number in range 0 to 1 double frand(){ return rand()/((double)RAND_MAX+1);}  //returns random floating point number in range 0 to f double frnd(float f){ return frand()*f;}  //returns 1 (true) at probability p//example://prob(0.7) will be true 70% of the time int prob(float p){ if(frand()<p)return 1; return 0;}   //returns distance between two points in 2 dimensions double dist2d(float x1,float y1,float x2,float y2){ float dx=x1-x2; float dy=y1-y2; return sqrt(dx*dx+dy*dy);}  //returns distance between two points in 3 dimensions double dist3d(float x1,float y1,float z1,float x2,float y2,float z2){ float dx=x1-x2; float dy=y1-y2; float dz=z1-z2; return sqrt(dx*dx+dy*dy+dz*dz);}   //Like % (modulus) but works "correctly" for negative values signed int zmod(signed int a,unsigned int b){ signed int c=0; if(!b)return c;//making sure we don't divide by zero if(a<0)--a; c=a%b; return c;}  //returns volume of sphere having radius r//the parentheses may help compiler optimize double spherevolume(float r){ return (M_PI*4/3)*(r*r*r);}  //returns surface area of sphere having radius r double spheresurface(float r){ return (M_PI*4)*(r*r);}` Subscribe to comments