#Downcast to c code#

It will go ahead and do the conversion though the base pointer might not be pointing to a derived object (as in your case). Static_cast relies on compile time information, so it really doesn't know the base pointer (you are trying to convert) actually points to a base object or a derived object. Now coming to static_cast and dynamic_cast. Only when you do this would it make sense. So when you want to use casting to convert a base pointer to a derived pointer, you must make sure the base pointer you are converting actually points to a derived class (as laserlight had stated). The other way around is not true, a derived pointer can't point to a base object - This is because a base object is NOT an object of the derived class.Ĭase2 is not permitted unless you do casting. This is because a derived object is also an object of the base class.

This would cause the correct values to be stored in visits_per_year.The result of a dynamic_cast is the one that is correct, explanation below:Ī base pointer can point to a derived object. Treated as a floating point number, which will cause the compiler to treat theĮxpression as if it were to result in a floating point number:įloat visits_per_year = pain_visits / (float)age įloat visits_per_year = (float)pain_visits / age The way to getĪround this problem is to cast one of the values being divided so it gets Unless the patient had an awful lot of visits to the doc. The problem is that when this program is run, visits_per_year will be zero * magical function returns the number of visits */įloat visits_per_year = pain_visits / age * magical function returns the age in years */ Perform is to compute the number of times per year of life someone has come in One operation you might conceivably want to Have a function to compute their age in years and the number of times For instance, if you were tracking heart patients, you might When might this come up? It's often reasonable to store two values in Kind of fancy division where we didn't want truncated values, we'd have toĬast one of the variables to a floating point type. Keep the result as a floating point number. Or even between one floating point number and an integer, is sufficient to On the other hand, it turns out that division between floating point numbers, Why? Well, 3/5 is less than 1, and integer division ignores the remainder. Of integers is itself treated as an integer: for instance, 3/5 becomes 0! That in C (and other programming languages), the result of the division So when would a typecast come in handy? One use of typecasts is toįorce the correct type of mathematical operation to take place. Since the char type is just a small integer,Īdding this typecast actually doesn't add any value! The compiler that we intended the value to be treated as a character when we Strange: when we passed the value of x to printf as a char, we'd already told If you were paying careful attention, you might have noticed something kind of * ASCII character that corresponds to the current number

* of (char) to typecast the x into a character which outputs the * Note the use of the int version of x to output a number and the use To do this, you will need to use to typecast to allow you to print out the integer as its character equivalent. For example, what if you want to create your own chart of all 128 ASCII characters. One use for typecasting for is when you want to use the ASCII characters.

#Downcast to c code#

Note that the %c below is the format code for printing a single character The equivalent of the number 65 (It should be the letter A for ASCII). It is going to give the character output of * The (char) is a typecast, telling the computer to interpret the 65 as aĬharacter, not as a number.