COP 3223H meeting -*- Outline -*-

* Boolean expressions

** Boolean values
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      BOOLEAN VALUES IN C

For purposes of conditionals
(if-statements, conditional expressions)
0
non-zero

With
#include <stdbool.h>
the type bool
and two values: 


------------------------------------------
        ... is considered false
        ... is considered true
        
        ... false, true
            false is defined as 0, true as 1

        _Bool is part of the C99 standard, 
        but for future portability use <stdbool.h>
        and bool instead of 0, 1, and _Bool

** Boolean Expressions
*** Boolean operators
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       OPERATORS ON BOOLEANS

Negation:
      !   like
      
Short-circuit operators:

      &&  like
      ||  like

true && B == 
false && B == 

true || B ==
false || B ==


Bit-wise operators

      &
      |
      ~
      ^

07 & 07 ==
05 & 07 ==
01 & 07 ==
00 & 00 ==

07 | 00 ==
05 | 07 ==
05 | 02 ==
05 | 03 ==
03 | 00 ==

~07 == 
~06 ==
~05 ==
~04 ==

------------------------------------------
    ... not in Python
    ... and in Python
    ... or in Python
    ... B
    ... false
    ... true
    ... B

   (& answers)
    ... 07
    ... 05
    ... 01
    ... 00

    (| answers)
    ... 07
    ... 07
    ... 07
    ... 07
    ... 03

    (~ answers, having declared these numbers as ints)
    ... 37777777770
    ... 37777777771
    ... 37777777772
    ... 37777777773
    etc...

*** Boolean-valued expressions
    You rarely need to write true or false explicitly in a program,
    because most boolean values arise from other expressions...
------------------------------------------
     BOOLEAN-VALUED EXPRESSIONS

Comparisons have _Bool values:

 2 < 3
 3 > 2
 2 == 2
 2 != 3
 !(2 == 3)
 3 <= 3
 2 <= 3
 3 >= 2
 3 >= 3
 

Be sure to use == for comparisons
 2 = 2  // error!

 int v = 0;
 if (v = v) {           // wrong!
     printf("true\n");
 } else {
     printf("false\n");
 }

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        Note the difference between == and = in C (as in Python)