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The Princeton Egg

The Princeton Egg. The Global Consciousness Project (video) Princeton Egg Website Our Egg:   PrincetonEgg.cpp. a few things will help us design our own Princeton Egg. a coin flipper. "for" loop boundaries. // int x is the for loop variable counting // coin flips: int x = 0;

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The Princeton Egg

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  1. The Princeton Egg The Global Consciousness Project (video) Princeton Egg Website Our Egg:   PrincetonEgg.cpp

  2. a few things will help us design our own Princeton Egg a coin flipper

  3. "for" loop boundaries // int x is the for loop variable counting // coin flips: int x = 0; for (x=1; x<=100; x=x+1) { cout << "X in for loop: " << x << endl; } cout << "X after for loop: " << x << endl;

  4. Domain of a variable for (int x=1; x<=100; x=x+1) { cout << "X in for loop: " << x << endl; } cout << "X after for loop: " << x << endl; // error, x not useable outside for loop

  5. #include <cstdlib> rand( ); - "pseudo" random number randomNumber = rand( )%10; // generate random number 0 thru 9 srand( int seed ); - seed the random number

  6. remember...calling a library function int ranNum; ranNum = rand( ) %2; // random one or zero The result of the library function is placed into ranNum. The rand()%2 function returns a random 0 or 1 as a “service”.

  7. getting a coin flip int seed = 0; int randomNumber = 0; cout << "type a number to seed generator"; cin >> seed; srand( seed ); randomNumber = rand( )%2; // 0 or 1

  8. two problems with rand( ) 1. random numbers are the same every time you run it (the algorithm starts at a consistant place) 2. rand( )%2 gives equally spaced 0s and 1s (not random for these low numbers)

  9. #include <ctime> • time( 0 ); - returns the number of seconds since Jan 1 1970. I have no idea why. But, not an integer, some mutant "time" string… • so: #include <ctime> #include <cstdlib> srand ( (int) time(0) ); // seed random number generator with time

  10. actually, time(0) is a "structure" • a structure, or "struct" in C++, is a meta-variable, that contains many variables… one main, and a number of auxiliary values • the "time" struct contains the number of seconds (its main value), but also month, day, date and year which we can access when we get good at this

  11. #include <iostream> #include <string > #include <math.h> #include <cstdlib> #include <ctime> using namespace std; int main( ) {

  12. Our Princeton Egg Elementary Statistics

  13. Design 1. Flip some coins: a lot of them, in a for loop - use rand to generate numbers 0-9. - 0-4 are heads, 5-9 are tails 2. Count the number of heads and the number of tails

  14. Design 3. abs(heads - tails) / 2 is the number of errant coin flips e.g. For 10 flips, if you get 6 heads and 4 tails, 6 - 4 / 2 = 1 coin flip was errant NOTE THAT THIS INVOLVES DIVIDING INTEGERS

  15. we will use Casting ints and doubles ARE interchangeable but we have to cast int x; double y; x = 10; y = (double)x;

  16. casting int numberOfFlips=0; int numberOfHeads=0; int numberOfTails=0; int diff = 0; // mistake double percentage = 0.0; diff = abs( numberOfHeads - numberOfTails )/2; // no division should EVER be done with integers

  17. best: all divisions done with doubles double diff = 0.0; diff = (double) (abs( numberOfHeads - numberOfTails )) /2.0; 4. Calculate total % of errant flips percentage = (diff/(double)(numberOfFlips)) * 100.0;

  18. Design 5. Finally, is percentage greater than 10%? - stay home

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