detailed explenation please :(
Author
What is the difference (in detail) between = and ==?
and what is the difference between this code
if(x = 3) and if(x == 3)?
no clue why this is confusing me so much, my book tells me but it is very bleak and says it in such a way that confuses the heck out of me.
This is not for homework or anything I'm teaching myself through books/internet referance.
ty :D!
x = 8 // this sets the varialbe x to a value of 8
x == 8 // this checks if x is equal to 8, and if so, then it is true
example use
x = 8;
if( x == 8 )
// do something since x equals 8
else
// do something since x does not equal 8
x == 8 // this checks if x is equal to 8, and if so, then it is true
example use
x = 8;
if( x == 8 )
// do something since x equals 8
else
// do something since x does not equal 8
Might want to not that in c++ it is legal to say
What this does is sets x to 5, and if it worked (and there's no reason it won't) it executed whatever is in the if. That is why there is a difference between equals, and comparisons.
It's generally not a good idea to change the value of a variable in an if(), but you can and that's why we differentiate!
if( x = 5 ) {}What this does is sets x to 5, and if it worked (and there's no reason it won't) it executed whatever is in the if. That is why there is a difference between equals, and comparisons.
It's generally not a good idea to change the value of a variable in an if(), but you can and that's why we differentiate!
Assuming C or C++.
Both of your examples are statements. A statement has a type and value.
Consider this:
In C/C++, a boolean is equivalent to an integer.
In an if block, this means the following:
Side effect of this allows for some interesting code:
s in this example is null-terminated string. Last character after d is 0.
While condition continues as long as the condition evaluates to true.
Given the previous rules, the following happens:
Both of your examples are statements. A statement has a type and value.
Consider this:
"Hello World";3;x=3;x==3;In C/C++, a boolean is equivalent to an integer.
In an if block, this means the following:
if (condition) {}if (x = 3) {}if (3) { // x has value of 3}if (x == 3) {}if (0) {}if (1) {}Side effect of this allows for some interesting code:
const char *s = "Hello World";int i = 0;while (char ch = s[i++]) { std::cout << ch;}s in this example is null-terminated string. Last character after d is 0.
While condition continues as long as the condition evaluates to true.
Given the previous rules, the following happens:
s[i++] // has value of character at given index, or 0 if we've reached end of stringch = s[i++] // assigns, the value of the expression is s[i++]char ch = s[i++] // stores the result of above statement in new variablewhile (char ch = s[i++]) // the while () will therefore continue until s[i++] is not 0Quote:Original post by Splinter of Chaos
What this does is sets x to 5, and if it worked (and there's no reason it won't) it executed whatever is in the if.
it always works. The statements will be executed only if x is non-zero.
I won't ALWAYS work, I guess.
If Antheus is right and
if( x = 3 ) is the same as if(3) { \\x=3 }
then
if( x=0 ) would be the same as if(0) {} else {//x=0}
I can't test any of this right now, though. I'm in the process of switching IDEs.
If Antheus is right and
if( x = 3 ) is the same as if(3) { \\x=3 }
then
if( x=0 ) would be the same as if(0) {} else {//x=0}
I can't test any of this right now, though. I'm in the process of switching IDEs.
ya, if you do something like
the code in between { } will never execute
if(x = 0){ ...code...}the code in between { } will never execute
Quote:Original post by Antheus
A statement has a type and value.
I don't think so. A statement is an expression with a semicolon appended to it. Once you have a statement, the type and value of the expression are lost. Your reasoning applies to the expressions, however.
x = 3
is of type int and has the value 3, and
x == 3
is of type int and has a value that represents true (i believe it's 1).
Note the "missing" semicolons.
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