Instructions (in C language)

Edit the file exp10to2.c and implement exp10ToExp2.

Your code should take the struct Number pointed by parameter "pn" and preserve the value v=mantissa2exp210exp10. The restrictions are as follows:

• mantissa should end up as a value that has bit 63 set. mantissa is a 64-bit unsigned integer.
• exp10 should be 0 when your algorithm is done.
• exp2 can be any integer (signed)
• the represented value v should be preserved as much as possible

Submit your program when you are done. If it is a single file, please name it "main.c", otherwise, rezip the whole folder and submit the zip file.

To run the program with your specific test input, do the following in CodeBlocks:

• put a break point at the end of exp10ToExp2, you can click slightly to the right of the line number to toggle breakpoint on a line.
• In the "Project" menu, click "set programs' arguments"
• In Program Arguments, enter the following without quotes:"-n 1.23e20" (obviously change the floating point number to the one that you should use), click OK
• when the program stops at the break point, you can examine the expressing *pn
• In the Debugger pane, you can type the following command without the quotes "print *pn", copy-and-paste the output to the HTML editor area

Here is a trace of an example (you have to figure out the loop structure):

./main -n 1.23456789e30 mantissa = 123456789, exp10 = 22, exp2 = 0 mantissa = 123456789, exp10 = 22, exp2 = 0 mantissa = 12345678900000000000, exp10 = 11, exp2 = 0 mantissa = 1543209862500000000, exp10 = 11, exp2 = 3 mantissa = 15432098625000000000, exp10 = 10, exp2 = 3 mantissa = 964506164062500000, exp10 = 10, exp2 = 7 mantissa = 9645061640625000000, exp10 = 9, exp2 = 7 mantissa = 1205632705078125000, exp10 = 9, exp2 = 10 mantissa = 12056327050781250000, exp10 = 8, exp2 = 10 mantissa = 1507040881347656250, exp10 = 8, exp2 = 13 mantissa = 15070408813476562500, exp10 = 7, exp2 = 13 mantissa = 941900550842285157, exp10 = 7, exp2 = 17 mantissa = 9419005508422851570, exp10 = 6, exp2 = 17 mantissa = 1177375688552856447, exp10 = 6, exp2 = 20 mantissa = 11773756885528564470, exp10 = 5, exp2 = 20 mantissa = 1471719610691070559, exp10 = 5, exp2 = 23 mantissa = 14717196106910705590, exp10 = 4, exp2 = 23 mantissa = 1839649513363838199, exp10 = 4, exp2 = 26 mantissa = 18396495133638381990, exp10 = 3, exp2 = 26 mantissa = 1149780945852398875, exp10 = 3, exp2 = 30 mantissa = 11497809458523988750, exp10 = 2, exp2 = 30 mantissa = 1437226182315498594, exp10 = 2, exp2 = 33 mantissa = 14372261823154985940, exp10 = 1, exp2 = 33 mantissa = 1796532727894373243, exp10 = 1, exp2 = 36 mantissa = 17965327278943732430, exp10 = 0, exp2 = 36 mantissa = 17965327278943732430, exp10 = 0, exp2 = 36 mantissa = 17965327278943732430, exp10 = 0, exp2 = 36

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number.h

#ifndef NUMBER_H #define NUMBER_H #include struct Number { int sign; uint64_t mantissa; int16_t exp10; int16_t exp2; };

#endif

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parse.h

#ifndef PARSE_H #define PARSE_H #include #include "number.h"

struct ParseState { const char *ptr; struct Number *pn; };

int parse(const char *str, struct Number *pn);

#endif

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exp10to2.h

#ifndef EXP10TO2 #define EXP10TO2 #include "number.h"

void exp10ToExp2(struct Number *pn);

#endif

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main.c

#include #include #include #include

#include "parse.h" #include "exp10to2.h"

int main(int argc, const char **argv) { const char *numberStr = NULL; struct Number n; int error = 0; --argc; ++argv; // skip name of executable itself while (!error && argc) { if (strcmp(*argv,"-n") == 0) { --argc; ++argv; if (argc) { numberStr = *argv; --argc; ++argv; } else { fprintf(stderr,"-n should be followed by a number "); error = 1; } } } if (!error && numberStr) { // no errors encountered parse(numberStr, &n); exp10ToExp2(&n); } return 0; }

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parse.c

#include "parse.h"

int parseSign(struct ParseState *pps) { int retValue = 0; switch (*pps->ptr) { case '+': ++pps->ptr; // skip, default sign is fine break; case '-': ++pps->ptr; // advance retValue = 1; break; default: break; } return retValue; }

int isDigit(const char p) { return (p >= '0') && (p <= '9'); }

uint64_t parseUnsignedInt(uint64_t n, struct ParseState *pps) { while (isDigit(*pps->ptr)) { n = n * 10 + (*pps->ptr - '0'); ++pps->ptr; } return n; }

void parseMantissa(struct ParseState *pps) { // after sign, parse the main part pps->pn->mantissa = 0; pps->pn->exp10 = 0; { const char *oldPtr = pps->ptr; pps->pn->mantissa = parseUnsignedInt(0,pps); if (oldPtr != pps->ptr) // pointer advanced { if (*pps->ptr == '.') { ++pps->ptr; const char *oldPtr = pps->ptr; pps->pn->mantissa = parseUnsignedInt(pps->pn->mantissa, pps); pps->pn->exp10 -= (pps->ptr - oldPtr); } } } }

int parse(const char *str, struct Number *pn) { struct ParseState ps; int error = 0; ps.ptr = str; ps.pn = pn; pn->exp10 = 0; pn->exp2=0; pn->sign = parseSign(&ps); { const char *oldPtr = ps.ptr; parseMantissa(&ps); if (oldPtr != ps.ptr) { if (*ps.ptr == 'e') { int expSign; uint64_t exp = 0; ++ps.ptr; expSign = parseSign(&ps); exp = parseUnsignedInt(exp, &ps); pn->exp10 += (expSign ? -exp : exp); } } else { error = 1; } } return error; }

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exp10to2.c

#include "number.h" #include "exp10to2.h"

void exp10ToExp2(struct Number *pn) { // in this function, convert the number pointed to b // pn from a base-10 mantissa and exponent to a base-2 // mantissa and exponent // divide into two main cases: when exp10 > 0, and when // exp10 < 0 }