Task

Define a function/method/subroutine which sorts a sequence ("table") of sequences ("rows") of strings ("cells"), by one of the strings. Besides the input to be sorted, it shall have the following optional parameters:





 ordering
 A function specifying the ordering of strings; lexicographic by default.
 column
 An integer specifying which string of each row to compare; the first by default.
 reverse
 Reverses the ordering.


This task should be considered to include both positional and named optional parameters, as well as overloading on argument count as in Java or selector name as in Smalltalk, or, in the extreme, using different function names. Provide these variations of sorting in whatever way is most natural to your language. If the language supports both methods naturally, you are encouraged to describe both.

Do not implement a sorting algorithm; this task is about the interface. If you can't use a built-in sort routine, just omit the implementation (with a comment).

See also:

 Named Arguments


#include <stdlib.h>
#include <stdarg.h>
#include <stdio.h>
#include <ctype.h>
#include <string.h>
 
typedef const char * String;
typedef struct sTable {
    String * *rows;
    int      n_rows,n_cols;
} *Table;
 
typedef int (*CompareFctn)(String a, String b);
 
struct {
   CompareFctn  compare;
   int   column;
   int   reversed;
} sortSpec;
 
int CmprRows( const void *aa, const void *bb)
{
   String *rA = *(String *const *)aa;
   String *rB = *(String *const *)bb;
   int sortCol = sortSpec.column;
 
   String left = sortSpec.reversed ? rB[sortCol] : rA[sortCol];
   String right = sortSpec.reversed ? rA[sortCol] : rB[sortCol];
   return sortSpec.compare( left, right );
}
 
/** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * tbl parameter is a table of rows of strings
 * argSpec is a string containing zero or more of the letters o,c,r
 * if o is present - the corresponding optional argument is a function which 
 *      determines the ordering of the strings.
 * if c is present - the corresponding optional argument is an integer that
 *      specifies the column to sort on.
 * if r is present - the corresponding optional argument is either 
 *      true(nonzero) or false(zero) and if true, the sort will b in reverse order
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
int sortTable(Table tbl, const char* argSpec,... )
{
   va_list vl;
   const char *p;
   int c;
   sortSpec.compare = &strcmp;
   sortSpec.column = 0;
   sortSpec.reversed = 0;
 
   va_start(vl, argSpec);
   if (argSpec)
      for (p=argSpec; *p; p++) {
         switch (*p) {
         case 'o':
            sortSpec.compare = va_arg(vl,CompareFctn);
            break;
         case 'c':
            c = va_arg(vl,int);
            if ( 0<=c && c<tbl->n_cols)
               sortSpec.column  = c;
            break;
         case 'r':
            sortSpec.reversed = (0!=va_arg(vl,int));
            break;
         }
      }
   va_end(vl);
   qsort( tbl->rows, tbl->n_rows, sizeof(String *), CmprRows);
   return 0;
}
 
void printTable( Table tbl, FILE *fout, const char *colFmts[])
{
   int row, col;
 
   for (row=0; row<tbl->n_rows; row++) {
      fprintf(fout, "   ");
      for(col=0; col<tbl->n_cols; col++) {
         fprintf(fout, colFmts[col], tbl->rows[row][col]);
      }
      fprintf(fout, "\n");
   }
   fprintf(fout, "\n");
}
 
int ord(char v)
{
    return v-'0';
}
 
/* an alternative comparison function */
int cmprStrgs(String s1, String s2)
{
    const char *p1 = s1; 
    const char *p2 = s2;
    const char *mrk1, *mrk2;
    while ((tolower(*p1) == tolower(*p2)) && *p1) {
       p1++; p2++;
    }
    if (isdigit(*p1) && isdigit(*p2)) {
        long v1, v2;
        if ((*p1 == '0') ||(*p2 == '0')) {
            while (p1 > s1) {
                p1--; p2--;
                if (*p1 != '0') break;
            }
            if (!isdigit(*p1)) {
                p1++; p2++;
            }
        }
        mrk1 = p1; mrk2 = p2;
        v1 = 0;
        while(isdigit(*p1)) {
            v1 = 10*v1+ord(*p1);
            p1++;
        }
        v2 = 0;
        while(isdigit(*p2)) {
            v2 = 10*v2+ord(*p2);
            p2++;
        }
        if (v1 == v2) 
           return(p2-mrk2)-(p1-mrk1);
        return v1 - v2;
    }
    if (tolower(*p1) != tolower(*p2))
       return (tolower(*p1) - tolower(*p2));
    for(p1=s1, p2=s2; (*p1 == *p2) && *p1; p1++, p2++);
    return (*p1 -*p2);
}
 
int main()
{
   const char *colFmts[] = {" %-5.5s"," %-5.5s"," %-9.9s"};
   String r1[] = { "a101", "red",  "Java" };
   String r2[] = { "ab40", "gren", "Smalltalk" };
   String r3[] = { "ab9",  "blue", "Fortran" };
   String r4[] = { "ab09", "ylow", "Python" };
   String r5[] = { "ab1a", "blak", "Factor" };
   String r6[] = { "ab1b", "brwn", "C Sharp" };
   String r7[] = { "Ab1b", "pink", "Ruby" };
   String r8[] = { "ab1",  "orng", "Scheme" };
 
   String *rows[] = { r1, r2, r3, r4, r5, r6, r7, r8 };
   struct sTable table;
   table.rows = rows;
   table.n_rows = 8;
   table.n_cols = 3;
 
   sortTable(&table, "");
   printf("sort on col 0, ascending\n");
   printTable(&table, stdout, colFmts);
 
   sortTable(&table, "ro", 1, &cmprStrgs);
   printf("sort on col 0, reverse.special\n");
   printTable(&table, stdout, colFmts);
 
   sortTable(&table, "c", 1);
   printf("sort on col 1, ascending\n");
   printTable(&table, stdout, colFmts);
 
   sortTable(&table, "cr", 2, 1);
   printf("sort on col 2, reverse\n");
   printTable(&table, stdout, colFmts);
   return 0;
}