teaching machines

CS 330 Lecture 12 – C

February 17, 2014 by Chris Johnson. Filed under cs330, lectures, spring 2014.

Agenda

• what ?s
• array/pointer duality
• scope in C vs. Java
• array allocation in C vs. Java
• call by value in C vs. Java
• new types
• enums in C vs. Java

Think About This

TODO

• Read Simon Tatham’s Descent into C: http://www.chiark.greenend.org.uk/~sgtatham/cdescent.
• Why does C not have a boolean type?
• Why does Java not have unsigned types?
• 1/4 sheet.

Code

atoi.c

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

int main(int argc, char **argv) {
  const char s[10000] = "534714"; 

  int s_as_int = 0;

  // Solved with array-thinking...
  for (int i = 0; i < strlen(s); ++i) {
    s_as_int *= 10;
    s_as_int += s[i] - '0';
  }

  // Solved with pointer-thinking...
  s_as_int = 0;
  for (char *c = s; *c != '\0'; ++c) {
    s_as_int *= 10;
    s_as_int += *c - '0';
  }

  printf("s_as_int: %d\n", s_as_int);

  return 0;
}

points.c

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

int main(int argc, char **argv) {
  double vertices[] = {
       0.2560344, 0.7008195, 0.309516,
       0.9977562, 0.1579919, 0.811734,
       0.9093718, 0.1702925, 0.754314,
       0.5427342, 0.8875533, 0.595991,
       0.8922929, 0.8357852, 0.653600,
       0.8543975, 0.1454883, 0.976032,
       0.3781706, 0.0057611, 0.754993,
       0.4160220, 0.3118013, 0.652116,
       0.5450121, 0.8648328, 0.309731,
       0.1296349, 0.6227086, 0.794076,
       0.7750567, 0.8990120, 0.870277,
       0.6404002, 0.7845455, 0.874627,
       0.8406608, 0.0757393, 0.408112,
       0.4229174, 0.4599141, 0.680888,
       0.6372424, 0.3462617, 0.318470,
       0.9495815, 0.6654377, 0.563382,
       0.1967725, 0.7708067, 0.136886,
       0.8724695, 0.9815157, 0.616252,
       0.0389801, 0.4078829, 0.542178,
       0.7192636, 0.8921647, 0.372246,
  };

  /* printf("Vertex %d - %f %f %f", 0, vertices[0], vertices[1], vertices[2]); */
  /* printf("Vertex %d - %f %f %f", 1, vertices[3], vertices[4], vertices[5]); */
  /* printf("%d", i); */

  for (int i = 0; i < 20; ++i) {
    printf("Vertex %d - %f %f %f\n", i, vertices[3 * i], vertices[3 * i + 1], vertices[3 * i + 2]);
  }

  double *vertex = vertices;
  for (int i = 0; i < 20; ++i) {
    printf("Vertex %d - %f %f %f\n", i, vertex[0], vertex[1], vertex[2]);
    vertex += 3;
  }

  int j = 17;
  {
    int j = 32;
    printf("j: %d\n", j);
  }

  return 0;
}

Scope.java

package lecture08;

public class Scope {
  public static void main(String[] args) {
    int[] args;
    int j = 17;
    {
      int k = 32;
    }
    System.out.println(k);
  }
}

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