CS102B - Lesson 7

Makefiles, Intro to Pointers

Instructor: Professor Hong

## Review & Questions

## Make Files - atof

## atof - in 1 file ``` #include <stdio.h> #include <ctype.h> // K&R Pg. 71 // atof: convert string s to double double atof(char s[]) { double val, power; int i, sign; for (i=0; isspace(s[i]); i++) // skip white space ; sign = (s[i] == '-') ? -1 : 1; if (s[i] == '+' || s[i] == '-') i++; for (val=0.0; isdigit(s[i]); i++) val = 10.0 * val + (s[i] - '0'); if (s[i] == '.') i++; for (power=1.0; isdigit(s[i]); i++) { val = 10.0 * val + (s[i] - '0'); power *= 10.0; } return sign * val / power; } int main() { char input[] = "-1.23"; printf("%f\n", atof(input)); return 0; } ```

## atof - in 2 files - atof.c and atof.h ``` #include <stdio.h> double atof(char s[]); ``` ``` #include <ctype.h> // K&R Pg. 71 // atof: convert string s to double double atof(char s[]) { double val, power; int i, sign; for (i=0; isspace(s[i]); i++) // skip white space ; sign = (s[i] == '-') ? -1 : 1; if (s[i] == '+' || s[i] == '-') i++; for (val=0.0; isdigit(s[i]); i++) val = 10.0 * val + (s[i] - '0'); if (s[i] == '.') i++; for (power=1.0; isdigit(s[i]); i++) { val = 10.0 * val + (s[i] - '0'); power *= 10.0; } return sign * val / power; } ```

## atof - in 2 files - main.c ``` #include <stdio.h> #include <atof.h> int main() { char input[] = "-1.23"; printf("%f\n", atof(input)); return 0; } ```

## atof - in 2 files - compiling ``` gcc -o main atof.c main.c -I. ```

## Simple Make File ``` # this will compile all files everytime make is run make: main.c atof.c atof.h gcc -o main main.c atof.c -I. # this will clean or remove compiled files so you can start fresh clean: rm -f *.o *.exe ``` * <code>make</code> * <code>make clean</code>

## Updated Make File ``` # Definitions for constants CC=gcc CFLAGS=-I. # This will create your final output using .o compiled files make: main.o atof.o $(CC) $(CFLAGS) -o main main.o atof.o # This will compile atof.c atof.o: atof.c atof.h $(CC) $(CFLAGS) -c atof.c # This will compile main.c with its dependency main.o: main.c atof.h $(CC) $(CFLAGS) -c main.c # This will clean or remove compiled files so you can start fresh clean: rm -f *.o *.exe ``` * This allows you to only recompile

## Make Files - Reverse Polish Calculator

## Calculator - All in 1 File ``` #include <stdio.h> #include <stdlib.h> // for atof() // K&R page 76-79 #define MAXOP 100 // max size of operand or operator #define NUMBER '0' // signal that a number was found int getop(char []); void push(double); double pop(void); // reverse Polish calculator int main() { int type; double op2; char s[MAXOP]; while ((type = getop(s)) != EOF) { switch (type) { case NUMBER: push(atof(s)); break; case '+': push(pop() + pop()); break; case '*': push(pop() * pop()); break; case '-': op2 = pop(); push(pop() - op2); break; case '/': op2 = pop(); if (op2 != 0.0) push(pop() / op2); else printf("error:zero divisor\n"); break; case '\n': printf("\t%.8g\n", pop()); break; default: printf("error: unknown command %s\n", s); break; } } return 0; } #define MAXVAL 100 // maximum depth of val stack int sp = 0; // next free stack position double val[MAXVAL]; // value stack // push: push f onto value stack void push(double f) { if (sp < MAXVAL) val[sp++] = f; else printf("error:stack full, can't push %g\n", f); } // pop:pop and return top value from stack double pop(void) { if (sp > 0) return val[--sp]; else { printf("error:stack empty\n"); return 0.0; } } int getch(void); void ungetch(int); // getop: get next operator or numeric operand int getop(char s[]) { int i, c; while ((s[0] = c = getch()) == ' ' || c == '\t') ; s[1] = '\0'; if (!isdigit(c) && c != '.') return c; // not a number i = 0; if (isdigit(c)) // collect integer part while (isdigit(s[++i] = c = getch())) ; if (c == '.') // collect fraction part while (isdigit(s[++i] = c = getch())) ; s[i] = '\0'; if (c != EOF) ungetch(c); return NUMBER; } #define BUFSIZE 100 char buf[BUFSIZE]; // buffer for ungetch int bufp = 0; // next free position in buf int getch(void) // get a (possibly pushed back) charater { return (bufp > 0) ? buf[--bufp] : getchar(); } void ungetch(int c) // push character back on input { if (bufp >= BUFSIZE) printf("ungetch:too many characters\n"); else buf[bufp++] = c; } ```

## Calculator in Multiple Files - main.c ``` #include <stdio.h> #include <stdlib.h> #include <calc.h> // K&R page 76-79 #define MAXOP 100 // max size of operand or operator // reverse Polish calculator int main() { int type; double op2; char s[MAXOP]; while ((type = getop(s)) != EOF) { switch (type) { case NUMBER: push(atof(s)); break; case '+': push(pop() + pop()); break; case '*': push(pop() * pop()); break; case '-': op2 = pop(); push(pop() - op2); break; case '/': op2 = pop(); if (op2 != 0.0) push(pop() / op2); else printf("error:zero divisor\n"); break; case '\n': printf("\t%.8g\n", pop()); break; default: printf("error: unknown command %s\n", s); break; } } return 0; } ```

## Calculator in Multiple Files - calc.h ``` #define NUMBER '0' // signal that a number was found void push(double); double pop(void); int getop(char []); int getch(void); void ungetch(int); ```

## Calculator in Multiple Files - stack.c ``` #include <stdio.h> #include <calc.h> #define MAXVAL 100 // maximum depth of val stack int sp = 0; // next free stack position double val[MAXVAL]; // value stack // push: push f onto value stack void push(double f) { if (sp < MAXVAL) val[sp++] = f; else printf("error:stack full, can't push %g\n", f); } // pop:pop and return top value from stack double pop(void) { if (sp > 0) return val[--sp]; else { printf("error:stack empty\n"); return 0.0; } } ```

## Calculator in Multiple Files - getop.c ``` #include <stdio.h> #include <ctype.h> #include <calc.h> // getop: get next operator or numeric operand int getop(char s[]) { int i, c; while ((s[0] = c = getch()) == ' ' || c == '\t') ; s[1] = '\0'; if (!isdigit(c) && c != '.') return c; // not a number i = 0; if (isdigit(c)) // collect integer part while (isdigit(s[++i] = c = getch())) ; if (c == '.') // collect fraction part while (isdigit(s[++i] = c = getch())) ; s[i] = '\0'; if (c != EOF) ungetch(c); return NUMBER; } ```

## Calculator in Multiple Files - getch.c ``` #include <stdio.h> #include <ctype.h> #include <calc.h> // getop: get next operator or numeric operand int getop(char s[]) { int i, c; while ((s[0] = c = getch()) == ' ' || c == '\t') ; s[1] = '\0'; if (!isdigit(c) && c != '.') return c; // not a number i = 0; if (isdigit(c)) // collect integer part while (isdigit(s[++i] = c = getch())) ; if (c == '.') // collect fraction part while (isdigit(s[++i] = c = getch())) ; s[i] = '\0'; if (c != EOF) ungetch(c); return NUMBER; } ```

## Calculator - Compiling ``` gcc -o main.exe main.c getch.c getop.c stack.c -I. ```

## Calculator - Make File ``` # Definitions for constants CC=gcc CFLAGS=-I. # This will create your final output using .o compiled files make: main.o stack.o getch.o getop.o $(CC) $(CFLAGS) -o main main.o stack.o getch.o getop.o stack.o: stack.c $(CC) $(CFLAGS) -c stack.c getch.o: getch.c $(CC) $(CFLAGS) -c getch.c getop.o: getop.c $(CC) $(CFLAGS) -c getop.c # This will compile main.c with its dependency main.o: main.c calc.h $(CC) $(CFLAGS) -c main.c # This will clean or remove compiled files so you can start fresh clean: rm -f *.o *.exe ```