Question

Are there any examples for a recursive function that calls an other function which calls the first one too ?

Example :

function1()
{    
    //do something 
    function2();
    //do something
}

function2()
{
    //do something 
    function1();
    //do something
}

Answer 1

Mutual recursion is common in code that parses mathematical expressions (and other grammars). A recursive descent parser based on the grammar below will naturally contain mutual recursion: expression-terms-term-factor-primary-expression.

expression
    + terms
    - terms
    terms

terms
    term + terms
    term - terms

term
    factor
    factor * term
    factor / term

factor
    primary
    primary ^ factor

primary
    ( expression )
    number
    name
    name ( expression )