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Performing operations between int and double

I have a homework assignment in basic C that asks me to evaluate certain expressions and then check my answers in a program. I can't seem to get any of these answers correctly by my own calculations ...

They want me to solve math problems using these variables:

int a = 2;
double b = 4.7;
int c = 3;
double d = 4.2;

Here's an example question:

int answer1 = b+a/c-d;

I understand that since it has an int operand then all variables are converted to integer, so it should look something like this:

(4 + 2) / (3-4)

I got -6 as my answer when I do it manually, but when I enter it as code it gives me an answer of 0. Can anyone explain this? Am I doing the wrong order of operations? I just don't understand how the computer gets 0 from this. This is the easiest question in my homework and I have no clue. Please, help!

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2 answers


Your expression

b+a/c-d

coincides with

b + (a/c) - d


Since both a

and c

are integers, the factor a/c

is computed using integer division. It gives 2/3 = 0

. So you have:

b - d

It is calculated using floating point, since b

and d

are double

. The result is 0.5, which is int

truncated to 0 when the result is assigned .

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Your orders of operations don't work a bit:

int answer1 = b+(a/c)-d; 

int tmp1 = a/c; ---> 2/3 --> 0
int answer1 = 4.7 + 0 - 4.2 ----> 0.5 --> 0


http://www.cplusplus.com/doc/tutorial/typecasting/

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