CHAPTER 4
=========

	 Operators                           Associativity
-------------------------------------------------------------
() ++(postfix) --(postfix)                   left to right
-------------------------------------------------------------
+(unary) -(unary) ++(prefix) --(prefix) !    right to left
-------------------------------------------------------------
*  /  %                                      left to right
-------------------------------------------------------------
+  -                                         left to right
-------------------------------------------------------------
<  <=  >  >=                                 left to right
-------------------------------------------------------------
== !=                                        left to right
-------------------------------------------------------------
&&                                           left to right
-------------------------------------------------------------
||                                           left to right
-------------------------------------------------------------
?:                                           right to left
-------------------------------------------------------------
=  +=  -=  *=  /=  etc                       right to left
-------------------------------------------------------------
,(comma operator)                            left to right

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Relational operators:

--------------------------------------------------
Declarations and initializations
--------------------------------------------------
char    c = `w';
int     i = 1, j = 2, k = -7;
double  x = 7e+33, y = 0.001;
--------------------------------------------------
Expression      Equivalent expression    Value
--------------------------------------------------
`a' + 1 < c     (`a' + 1) < c            1 
-i-5*j >= k+1   ((-i)-(5*j)) >= (k+1)    0
3 < j < 5       (3<j) < 5                1
x-3.333<=x+y    (x - 3.333) <= (x+y)     1
x < x + y       x<(x+y)                  0
--------------------------------------------------


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Equality operators:

--------------------------------------------------
Declarations and initializations
--------------------------------------------------
int  i = 1, j = 2, k = 3;
--------------------------------------------------
Expression      Equivalent expression    Value
--------------------------------------------------
i == j          j == i                   0
i != j          j != i                   1
i+j+k==-2*-k    ((i+j)+k)==((-2)*(-k))   1
--------------------------------------------------


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Logical operators:

--------------------------------------------------
Declarations and initializations
--------------------------------------------------
char    c = `A';
int     i = 7, j = 7;
double  x = 0.0, y = 2.3;
--------------------------------------------------
Expression      Equivalent expression    Value
--------------------------------------------------
! c             ! c                      0
! (i - j)       ! (i - j)                1
! i - j         (!i) - j                -7
! !(x + y)      ! (!(x + y))             1
! x * !! y      (!x) * (!(!y))           1
--------------------------------------------------

 
--------------------------------------------------
Declarations and initializations
--------------------------------------------------
char    c = `B';
int     i = 3, j = 3, k = 3;
double  x = 0.0, y = 2.3;
--------------------------------------------------
Expression         Equivalent expression    Value
--------------------------------------------------
i && j && k        (i && j) && k              1
x || i && j-3      x || (i && (j-3))          0
i<j && x<y         (i < j) && (x<y)           0
i<j || x<y         (i<j) || (x<y)             1
`A'<=c&&c<=`Z'     (`A'<=c)&&(c<=`Z'  )       1
c-1==`A'||c+1==`Z' ((c-1)==`A')||((c+1)==`Z') 1 
--------------------------------------------------


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Short-circuit evaluation
------------------------

int    cnt = 0;

while  (++cnt <= 3 && (c = getchar()) != EOF) {
   .....      /* do something */


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Dangling else:
--------------

if (a == 1)
   if (b == 2)
      printf("***\n");
   else
      printf("###\n");
----------------------------

if (a == 1)
   if (b == 2)
      printf("***\n");
else
   printf("###\n");

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

(count.c)

/* Count blanks, digits, letters, newlines, and others. */

#include <stdio.h>

int main(void)
{
   int   blank_cnt = 0, c, digit_cnt = 0,
         letter_cnt = 0, nl_cnt = 0, other_cnt = 0;

   while ((c = getchar()) != EOF)     /* braces not necessary */
      if (c == ' ')
         ++blank_cnt;
      else if (c >= '0' && c <= '9')
         ++digit_cnt;
      else if (c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z')
         ++letter_cnt;
      else if (c == '\n')
         ++nl_cnt;
      else
         ++other_cnt;

   printf("%10s%10s%10s%10s%10s%10s\n\n",
      "blanks", "digits", "letters", "lines", "others", "total");
   printf("%10d%10d%10d%10d%10d%10d\n\n",
      blank_cnt, digit_cnt, letter_cnt, nl_cnt, other_cnt,
      blank_cnt + digit_cnt + letter_cnt + nl_cnt + other_cnt);
   return 0;
}

--------------------------------------------------------------------

    blanks    digits   letters     lines    others     total

      208        32       361        27       180       808

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

For loops:
----------

i = 1;
sum = 0;
for ( ; i <= 10; ++i)
    sum += i;
----------------------------

i = 1;
sum = 0;
for ( ; i <= 10; )
    sum += i++;
----------------------------

i = 1;
sum = 0;
for ( ; ; ) {
    sum += i++;
    printf("%d\n", sum);
}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

The comma operator:
-------------------

for (sum = 0, i = 1; i <=n; ++i)
   sum += i;


for (sum = 0, i = 1; i <= n; sum += i, ++i)
   ;

but not as

for (sum = 0, i = 1; i <= n; ++i, sum += i)
   ;


--------------------------------------------------
Declarations and initializations
--------------------------------------------------
int     i, j, k = 3;
double  x = 3.3;
--------------------------------------------------
Expression       Equivalent expression    Value
--------------------------------------------------
i=1, j=2, ++k+1  ((i=1),(j=2)),((++k)+1)  5
k!=1,++x*2.0+1   (k!=1),(((++x)*2.0)+1)   9.6 
--------------------------------------------------

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

do-while:
---------

do {
   printf("Input a positive integer: ");
   scanf("%d", &n);
   if (error = (n <= 0))
      printf("\nERROR; Do it again!\n\n");
} while (error);


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Break & continue:
-----------------

while (1) {
   scanf("%1f", &x);
   if (x < 0.0)
      break;        /* exit loop if x is negative */
   printf("%f\n", sqrt(x));
}
/* break jumps to here */



for (i = 0; i < TOTAL; ++i) {
   c = getchar();
   if (c >= `0' && c <= `9')
      continue;
   .....          /* process other characters */
/* continue transfers control to here to begin next iteration */
}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Switch:
-------

switch (c) {
case `a':
   ++a_cnt;
   break;
case `b':
   ++b_cnt;
   break;
case `c':
case `C':
   ++cC_cnt;
   break;
default:
   ++other_cnt;
}
 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

The conditional operator:

-------------------------------------------------------
Declarations and initializations
-------------------------------------------------------
char    a = `a', b = `b';  /* a has decimal value 97 */
int     i = 1, j = 2;
double  x = 7.07;
-------------------------------------------------------
Expression   Equivalent expression  Value Type
-------------------------------------------------------
i==j?a-1:b+1  (i==j)?(a-1):(b+1)     99    int
j%3==0?i+4:x ((j%3)==0)?(i+4):x     7.07  double  
j%3?i+4:x    (j%3)?(i+4):x          5.0   double   
-------------------------------------------------------