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Direct, Pointer and Reference access to variables
Further C++ Object Oriented features example from a Well House Consultants training course
More on Further C++ Object Oriented features [link]
Source code: alias.cpp Module: C234
#include <iostream>
using namespace std; /* Direct, Pointer and Reference access to variables Pointers (declared with a "*") provide indirect access to a variable through its address - which is very useful if you want to pass a large and/or complex piece of data into a function, or access it via a single, simple name, without having to duplicate a whole lot of things. Pointers, though, lead to their own extra complexities with * and & and (), . and -> turning up all over the place. References can displace pointer use in some circumstances - they're a lightweight alternative, if you like to think of them like that. Or you can think of them as aliases - another name - for a variable. This name can be applied dynamically within a block in place of the more complex name, but any assignment back to it will then alter the value in the variable rather that where it aliases ... the only way to change where it aliases is to let it go out of scope and re-define it; very often that will be done via a single declaration at the top of a loop block. */ int main(int argc, char ** argv) { int number = 34; // value variable int * wherenum = &number; // address of the value variable int & alsonum = number; // another name for value variable number++; alsonum++; (*wherenum)++; cout << number << endl; cout << *wherenum << endl; cout << alsonum << endl << endl; // When would I do THAT? int ages[5]; ages[0] = 23; ages[1] = 32; ages[2] = 21; ages[3] = 42; ages[4] = 33; for (int i=0; i<50; i+=10) { cout << ages[i/10] << endl; // ages[i/10] gets scruffy if repeated a lot int &altern = ages[i/10]; // altern provides an alias here ... cout << altern << endl; // lightweight alternitive to a pointer int *nother = &ages[i/10]; // here is how it works with a pointer cout << *nother << endl << endl; } } /* Sample output ... munchkin:c5 grahamellis$ ./alli 37 37 37 23 23 23 32 32 32 21 21 21 42 42 42 33 33 33 munchkin:c5 grahamellis$ */ Learn about this subject
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