5.11.c

@@ -0,0 +1,150 @@
+// Exercise 1-21. Write a program entab that replaces strings of blanks by the minimum number of tabs and blanks to achieve the same spacing
+
+// Exercise 5-11. Modify the program entab and detab (written as exercises in Chapter 1) to accept a list of tab stops as arguments. Use the default tab settings if there are no arguments. 
+
+// Use the same tab stops as for detab. When either a tab or a single blank would suffice to reach a tab stop, which should be given preference? 
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+int getfine(char* s, int maxline);
+int divides (int a, int b);
+void spaces (char *in, char *out);
+void detab (char *in, char *out, int stops);
+   /* getline:  read a line into s, return length  */
+   int getfine(char* s, int maxline)
+   {
+       int c, i;
+       for (i=0; ((c=getchar())!=EOF) && c!='\n'; i++)
+       {
+           *s = c;
+           s++;
+       }
+       if (c == '\n')
+       {
+           *s = 0;
+           ++i;
+       }
+       //printf("%d : len \n",i);
+       return i;
+
+   }
+
+int MAXSIZE=10000;
+int HOWBIGISTAB=8;
+int OFFSET=0;
+
+int main(int argc, char *argv[])
+{
+  //  while (argv!=0 && *argv!=0)
+  //  {argv--;}
+  // -m
+  argv++;
+  if (argc > 1)
+    {
+      while (argv!=0 && *argv!=0)
+        {
+          if (*argv[0]=='+')
+            {
+              char temp[MAXSIZE];
+              strcpy(*argv,temp);
+              temp[0]=0; //get rid of +
+              argv++;
+              HOWBIGISTAB=atoi(temp);
+              continue;
+            }
+          if (*argv[0]=='-')
+            {
+              char temp[MAXSIZE];
+              strcpy(*argv,temp);
+              temp[0]=0; //get rid of -
+              argv++;
+              OFFSET=atoi(temp);
+              continue;              
+            }
+          argv++;
+        }
+    }
+  
+  char c;
+  int count=0;
+  char foo[MAXSIZE];
+  char bar[MAXSIZE];
+  int maxsize=MAXSIZE;
+   getfine(foo,maxsize);
+  //  spaces (foo, bar);
+  detab (foo, bar, 8);       
+  printf ("bar: %s ", bar);
+  return (0);
+}
+
+
+int divides (int a, int b)
+{
+  if (b==0) return 1; //arbitrary
+  return !(a % b == 0);
+}
+
+
+void spaces (char *in, char *out)
+{
+  int tabs = 0;
+  int spaces = 0 ;
+  int count=0;
+  for (; (count < MAXSIZE) && (*in == ' '); count++); //count the spaces in foo
+
+  if (divides(HOWBIGISTAB,count)) //do we need remainder?
+    {
+      tabs=count/HOWBIGISTAB;
+      spaces=0;
+    }
+  else
+    {
+      tabs=count/HOWBIGISTAB;
+      spaces=count%HOWBIGISTAB;
+    }
+
+  int i=0;
+  for (; i<tabs; i++)
+    {
+      *out='\t';
+      out++;
+    }
+  for (; i<spaces; i++)
+    {
+      *out=' ';
+      out++;
+    }
+}
+
+
+
+void detab (char *in, char *out, int stops)
+//input, a string with possibly some tabs
+//output, a string that has, wherever there's a tab, it justifies to the next 'tab stop', which occur every 'stops' spaces.
+{
+  int pos=0;
+  while (in!=0)
+    {
+      if (*in == 0) break;
+
+      if (*in == '\t')
+        { // we justify to the next spot in 'out', adding
+          while (!divides(stops, pos) && (pos > OFFSET)) //are we not at a stop?
+            {
+              pos++;
+              *out=' ';
+              out++;
+            }
+          // we are at a stop now, stop adding spaces
+          in++;
+        }
+      else
+        {
+          *out=*in;
+          out++; //gotta also overwrite something other than the first output character
+          pos++;
+          in++; //next symbol                    
+        }
+    }
+}