/// WEEK 11 **

/// mutate a string of text to the desired string

/// Dawkins' evolving words/letters example

/// not sure yet how to feed in starting string from command line, Jeremy will go over this next week

/// currently must go in and edit value of "target"

// ************ the infinite monkey example, evolve strings, how to change one word into another through intermediate words

// create a random initial sequence

// mutate a sequence of letters and numbers

// need to know if we're getting closer to our target sequence or not: compare strings

//calculate for a pair of strings, the number of mismatches between them

// or could break something up by words and see where those match

// or could slide two characters along each other and see where the best match is

// or can do that with allowing gaps in the middle which is basically a BLAST search

//to split a string into words is to "tokenize" a string

//evolve

// to write the code, best to put those tasks that are repeated into functions:

//produce random character - FUNCTION

//compare strings - FUNCTION

//create initial sequence - MAIN

//evolve - MAIN

#include <stdio.h>

#include <stdlib.h>

#include <time.h>

#include <math.h>

#include <string.h>

// make a static variable so that this value is defined throughout the whole extent of the program

static int length;

int rand_between(int max) { // return a random int between 0 and max-1, i.e will never get a number = to max, only max-1

return rand() % max;

}

char randChar(){ //produce a random character, to: 1. mutate and 2. to create our initial random sequence

char finalChar;

int choices = 26*2+4; //length of our library of all possible characters, see comments in MAIN

int draw = rand_between(choices-1); // minus 1 because 52 is going from 0 to 51

//make letters out of the numbers we drew

if(draw < 26) finalChar = 'a'+draw; // so 0-25 in our library is now lowercase a-z

else if(draw < 52) finalChar = 'A'+(draw-26);//if 26-51, then it's an uppercase letter A-Z

else{

//use a switch statement, in some situations, where there are lots of choices, it's better than a bunch of if statements

switch(draw){ //C will look at draw and then proceed into one of the things following in the curly brackets

//so these are all case statements: case, value of draw, colon, do everything here

case 52: finalChar = '\''; // need to escape into the apostrophe because otherwise C would read it as a single quote

break; // NEED these here because the switch statement goes to the matching 'case' then proceeds through all following unless the breaks stop it

case 53: finalChar = '!';

break;

case 54: finalChar = ' ';

break;

case 55: finalChar = '.';

break;

}

}

return(finalChar);

}

int stringEval(char *s1, char *s2){ // make our "evaluate" function

//string 1 and 2 are fed in to the function

//get length of strings -- this was defined globally as a static variable

//hamming distance

int hdist =0;

int i;

for(i = 0; i < length; i++){ // go through all the spots in the string

if(s1[i]!=s2[i]) hdist++; // if a spot doesn't match between the 2 strings, add 1 to dist, ot get our final Haming distance at the end

}

return(hdist);

}

// alternatively could make the library manually then call random pieces of it to get the random character

//char choices[]="abcdefghijklmnopqrstuvwxyABCDEFGHIJKLMNOPQRSTUVWXYZ. '!";

int main(int argc,const char *argv[]){

// set seed for random number generator

unsigned int seed = (unsigned int)time(NULL);

srand(seed);

//printf("%d\n",seed);

// what is the starting string

char target[]="Target string";

length = (int)strlen(target); // use length of string function, cast it as an int because otherwise it's an unsigned int

//strlen doesn't include the /0 in the length of the string

//make a random starting sequence of letters

char *startString = malloc((length+1)*sizeof(char)); /// BECAUSE strlen doesn't include the /0 in the length of the string

int i;

for(i=0; i < length; i++){

startString[i]= randChar();

}

startString[length]='\0'; /// BECAUSE the array starts with a zero and goes to length (rather than length-1) then we just put the null character in there

int muts = 0; //how many mutations happen to get to the target sequence

int mutationsAtMismatches;

while(stringEval(startString, target)>0){ // evolve the string of characters

//mutate

int site;

do{

site = rand_between(length);

muts++;

}while(startString[site]==target[site]);

startString[site]=randChar();

//evaluate how close the two strings are -- Hamming distance ( sum over units for if 1 when units are different and 0 if same )

//--inherent in the loop

//decide --inherent in the loop

//stop when we get the phrase we want--inherent in the loop

mutationsAtMismatches++;

printf("%s \n", startString); //Print mutations to console as they happen

}

printf("Number of mutations to target= %d \n", mutationsAtMismatches); //print the number of steps it takes to get to the target sequence

}