va_list with multiple types

i want to write soemthing like this:
a function which will print various types of arguments.
I tried to work with va_list, it doesn't work.
int main(){
write("this ",1.2," is ",'a',7," test");
}
should result in:
this 1.2 is a7 test

If C does not store RTTI why is there a need for casting from type to type(except BDSM)?