Stuff

 register int p, op=2; register float c=atof(argv[1]);                                   // Parameters.
 for(p=2; p<argc; ++p) {                                                                 // Loop through parameters.
  if(atof(argv[p])==0) {                                                                 // Check if we want to change operator.
   if(!strcmp(TLIB_ARITH_PLS,argv[p])) { op = 1; continue; }                             // Change operator: Addition.
   if(!strcmp(TLIB_ARITH_MIN,argv[p])) { op = 2; continue; }                             // Change operator: Substraction.
   if(!strcmp(TLIB_ARITH_MUL,argv[p])) { op = 3; continue; }                             // Change operator: Multiplication.
   if(!strcmp(TLIB_ARITH_DIV,argv[p])) { op = 4; continue; }                             // Change operator: Division.
  }
  switch(op) {                                                                           // Check current operator.
   case 1: c += atof(argv[p]); break;                                                    // Operate: Addition.
   case 2: c -= atof(argv[p]); break;                                                    // Operate: Substraction.
   case 3: c *= atof(argv[p]); break;                                                    // Operate: Multiplication.
   case 4: c /= atof(argv[p]); break;                                                    // Operate: Division.
  }}