help: simple problem

hi,

just started c prog for college. useless at it. need help finding out what this comes to.its for exam.

three parts:

a =3, b=2, c=4,

what values of following if legal:


b<a<c

a*b%c+3

--b*c+a


need help especially with --b;

also what does <<a or >>a mean

Quote:

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Originally Posted by screamer903

need help especially with --b;

---

-- is unary decrement operator which evaluates to

Code:

---

--b;//same as
b = b -1;

---

So, it'll decrement the value of b first and then only will it return the final value of b.

Quote:

---

Originally Posted by screamer903

also what does <<a or >>a mean

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Have a look at the shift operators explanation in the FAQs then if there is something specific you're unclear about post back.

>b<a<c
Legal, but it doesn't do what you may expect. At first glance one might expect this to say "true if b is less than a and a is less than c", but in reality it compares the boolean result of b < a (0 or 1) to c. b is 2 and a is 3, so b < a is true. c is 4, so 1 < 4 is also true.

>a*b%c+3
This is an easy one, all operations go from left to right. So it's:

Code:

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( ( 3 * 2 ) % 4 ) + 3

---

>>the boolean result of b < a (0 or 1)
I was always under the impression that true was represented as anything nonzero, and that it wasn't guaranteed to be 1. That would mean that the statement is totally unpredictable, but I probably missed something somewhere. :p

Quote:

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Originally Posted by XSquared

I was always under the impression that true was represented as anything nonzero

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"On input":
http://www.eskimo.com/~scs/C-faq/q9.2.html

>I was always under the impression that true was represented as anything nonzero
Correct. True is non-zero and false is zero. However, boolean expressions are well defined and always evaluate to either 0 or 1.

It makes for neat little tricks like replacing:

Code:

---

if(a > b)
  c++;

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with:

Code:

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c += a > b;

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:D

That's not nearly as practical as my brilliant binary search tree trick:

Code:

---

struct node {
  T data;
  struct node *link[2];
};

struct node *insert ( struct node *tree, T data )
{
  if ( tree == NULL ) {
    tree = make_node ( data );
  } else {
    int dir = data > tree->data;
    tree->link[dir] = insert ( tree->link[dir], data );
  }

  return tree;
}

---

;) It gets better and better as the symmetric cases get longer and longer.

a*b%c+3

in this apply the BOMDAS rule
that is bracket
of
multiply
divide
add
substract

--b*c+a
--b will decrease the value od b by one unit
the remaining will Follow bomdas rule

>>a and <<a are the right shift and left shift operators which will shift the binary blase either right or left

for example,
10 = 1010(in binart system)
>> 10= 0101 =5 (here, the binary digits got shifted to a place right)