Name resolution (programming languages): Difference between revisions

Revision as of 13:28, 18 December 2019

Revision as of 19:36, 13 April 2020

Line 41:

For example, the parameter "foo" shadows the local variable "foo" in this common pattern:

<source lang="java">

private int foo; // Name "foo" is declared in the outer scope

public void setFoo(int foo) { // Name "foo" is declared in the inner scope, and is function-local.

this.foo = foo; // Since "foo" will be first found (and resolved) in the ''innermost'' scope,

// in order to successfully overwrite the stored value of the attribute "foo"

// with the new value of the incoming parameter "foo", a distinction is made

// between "this.foo" (the object attribute) and "foo" (the function parameter).

}

}

public int getFoo() {

return foo;

}

}

</source>

Name masking can cause [[Function overloading#Complications|complications in function overloading]], due to overloading not happening across scopes in some languages, notably C++, thus requiring all overloaded functions to be redeclared or explicitly imported into a given namespace.

Line 62:

For example, in this code:

<source lang="cpp">

class Point {

private:

double x, y;

public:

Point(double x, double y) { // x and y declared here mask the privates

setX(x);

setY(y);

}

public:

void setX(double newx) { x = newx; }

Point(double x, void setY(double newyy) { // x and y =declared here mask newy;the }privates

setX(x);

setY(y);

}

void setX(double newx) { x = newx; }

void setY(double newy) { y = newy; }

}

</source>

within the <tt>Point</tt> constructor, the class variables <tt>x</tt> and <tt>y</tt> are [[Variable shadowing|shadowed]] by local variables of the same name. This might be alpha-renamed to:

<source lang="cpp">

class Point {

private:

double x, y;

public:

Point(double a, double b) {

setX(a);

setY(b);

}

void setX(double newx) { x = newx; }

void setY(double newy) { y = newy; }

}

void setX(double newx) { x = newx; }

void setY(double newy) { y = newy; }

}

</source>

In the new version, there is no masking, so it is immediately obvious which uses correspond to which declarations.