» CS 330 Lecture 13 – Strings and structs

CS 330 Lecture 13 – Strings and structs

February 20, 2012 by Chris Johnson. Filed under cs330, lectures, spring 2012.

Agenda

array out-of-bounds
strings null-terminated char arrays

strlen
strcat
strcpy
strdup
strcmp

structs
header files
a stack API
evaluating postfix expressions

for each token

if token is number, push it on operand stack
if token is operator, pop two operands, push result back on

pop stack to get the value

Code

makefile

EXES = first arrays months oob strings

all: $(EXES)

$(EXES): %: %.c
	gcc -o $@ -Wall -std=c99 $<

clean:
	rm -f $(EXES)

oob.c

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv) {

  double nums[100];

  for (int i = 0; i < 5; ++i) {
    nums[i] = rand() / (float) RAND_MAX;
  }

  return 0;
}

strings.c

#include <stdio.h>
#include <stdlib.h>

/* ------------------------------------------------------------------------- */

/* int strlen(const char *s) { */
  /* for (int i = 0; i <  */
  /* int i = 0; */
  /* while (s[i] != '\0') { */
    /* i++; */
  /* } */
  /* return i; */
/* } */

/* ------------------------------------------------------------------------- */

int strlen(const char *s) {
  const char *ps = s;
  int i = 0;
  while (*ps != '\0') {
    i++;
    ps++;
  }
  return i;
}

/* ------------------------------------------------------------------------- */

int main(int argc, char **argv) {

  char name[] = "Jeff"; 

  /* name[0] = 'J'; */
  /* name[1] = 'e'; */
  /* name[2] = 'f'; */
  /* name[3] = 'f'; */
  /* name[4] = '\0'; // name[4] = 0; */
  /* name[4] = 'a'; // name[4] = 0; */

  printf("name: %s\n", name);
  printf("strlen(name): %d\n", strlen(name));

  return 0;
}

stack.h

#ifndef STACK_H
#define STACK_H

struct stack_t {
  int elements[100];
  int top;
}

struct stack_t *make_stack();

// Add element to stack
void push(int new_thing);

int pop();

int peek();

#endif

stack.cpp

#include "stack.h"

struct stack_t *make_stack() {
  struct stack_t *new_stack = malloc(sizeof(struct stack_t));
  new_stack->elements = ;
  new_stack->top = 0;
}

Haiku

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