111CMSC 212 – S07 (lect 14)AnnouncementsExam #1 – Was returned in section on Monday– Re-grade requests due by next Monday (yes first day of spring break)Reading– Chapter 16, 13.3 (Today)• Skip 16.4-16.616,9– Chapter 17 (Thursday)2CMSC 212 – S07 (lect 14)Project #3 HintsApproach– Start with assembler• Skips labels until rest is working– Move onto executeParsing– Use tokenize routineLabels– Think about how to handle• Labels defined before use• Labels defined after use223CMSC 212 – S07 (lect 14)Additional Standard Library FunctionsRandom Numbers– void srand(unsigned int);• seed the random number generator– int rand(void);• return a pseudo-random number between 0 and RAND_MAX– used with a time function makes it closer to actually random• time_t time(time_t *returned_value);Floating Point (all use doubles)– prototypes defined in math.h– double sqrt(double value);• compute square root of value• Bad parameters produce domain errors• stderr is set to EDOM– double pow(double x, double y)• returns the value of x raised to the y power– double exp(double value)• computes evalue– double log(double value) and double log10(double value)• base e logarithm and base 10 logarithm4CMSC 212 – S07 (lect 14)Trig Functionsdouble sin(double angle);– computes sin of angle (in radians)Also have:– double cos(double angle);– double tan(double angle);– double asin(double value);– double acos(double value);– double atan(double value);335CMSC 212 – S07 (lect 14)Other Handy FunctionsFractions– double floor(double x);• next lowest whole integer– double ceil(double x);• next highest whole integer– double fabs(double x);• absolute value– double fmod(double x, double y);• restricts y to an integer6CMSC 212 – S07 (lect 14)Function PointersPointers can also be of type function– void (*myVoidFunc)(int);• declare a variable myVoidFunc which points to a function which takes an integer as a parameter.• Like any pointer variable, declaring it does not create an instance of what it points to!Uses– Create Object Oriented Code– Callbacks from utility routinesOften a good idea to typedef each function pointer– typedef void(*myVoidFuncPtr)(int);447CMSC 212 – S07 (lect 14)Function Pointer Exampleunion myDataType {int a;float b;} ;typedef void (*myPrintFuncPtr)(union myDataType);typedef struct {myPrintFuncPtr printIt;union myDataType data;} myObject ;void printInt(union myDataType data) {printf("data = %d\n", data.a);}8CMSC 212 – S07 (lect 14)Function Pointer Example Continuedint main(void) {int i;myObject *objects;objects = (myObject *) calloc(sizeof(myObject), 5);objects[0].data.a = 43;objects[0].printIt = printInt;objects[1].data.b = 3.1415;objects[1].printIt = printFloat;for (i=0; i < 2; i++) {objects[i].printIt(objects[i].data);}exit(0);}559CMSC 212 – S07 (lect 14)Callback Exampletypedef int (*compareFunc)(item *a, item * b);int searchTree(Node *root, Item *target, compareFunc cmp) {if (!root) return -1;ret = (cmp)(a, root->data);if (ret == 0) {/* found it */return 1;} else if (ret < 0) {return searchTree(root->left, target, cmp);} else {return searchTree(root->right, target, cmp);}}10CMSC 212 – S07 (lect 14)Date & Time Functionsclock_t clock(void);– process time since start of program execution– to convert to time, use CLOCKS_PER_SECtime_t time(time_t *val);– fill val with the current time (in machine dependent format)char *ctime(time_t *val);– return a character representation of the passed time– Sun Jul 4 04:02:48 2005\n\0double difftime(time_t time1, time_t time2)– return number of seconds between time1 and time2struct tm *gmtime(time_t val)struct tm*localtime(time_t val)– convert to UTC or local time6611CMSC 212 – S07 (lect 14)Execution EnvironmentProgram Termination– abort(void);• terminate program with error (usually a core time)– atexit(void (func)(void));• on termination call function func– exit(int status);Running Shell Commands– void system(char *command);• runs command (not all systems support it)Sorting– void qsort(void *base, size_t number, size_t elementSize, int (*compare)(void const *, void const *));• Sort the passed array, using passed compare function• strcmp will work for
View Full Document
Unlocking...