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A basic example is in the argv argument to the main function in C (and C++), which is given in the prototype as char **argv—this is because the variable argv itself is a pointer to an array of strings (an array of arrays), so *argv is a pointer to the 0th string (by convention the name of the program), and **argv is the 0th character of the ...
On many common platforms, this use of pointer punning can create problems if different pointers are aligned in machine-specific ways. Furthermore, pointers of different sizes can alias accesses to the same memory, causing problems that are unchecked by the compiler. Even when data size and pointer representation match, however, compilers can ...
function factorial (n is a non-negative integer) if n is 0 then return 1 [by the convention that 0! = 1] else if n is in lookup-table then return lookup-table-value-for-n else let x = factorial(n – 1) times n [recursively invoke factorial with the parameter 1 less than n] store x in lookup-table in the n th slot [remember the result of n! for ...
This is in contrast to binary operations, which use two operands. [2] An example is any function : , where A is a set; the function is a unary operation on A. Common notations are prefix notation (e.g. ¬, −), postfix notation (e.g. factorial n!
With these definitions, one can compute, say 6! at compile time using the expression Factorial<6>::value. Alternatively, constexpr in C++11 / if constexpr in C++17 can be used to calculate such values directly using a function at compile-time:
Dim counter As Integer = 5 ' init variable and set value Dim factorial As Integer = 1 ' initialize factorial variable Do While counter > 0 factorial = factorial * counter counter = counter-1 Loop ' program goes here, until counter = 0 'Debug.Print factorial ' Console.WriteLine(factorial) in Visual Basic .NET
The C and C++ syntax given above is the canonical one used in all the textbooks - but it's difficult to read and explain. Even the above typedef examples use this syntax. However, every C and C++ compiler supports a more clear and concise mechanism to declare function pointers: use typedef, but don't store
The simplicity of this computation makes it a common example in the use of different computer programming styles and methods. [76] The computation of ! can be expressed in pseudocode using iteration [77] as define factorial(n): f := 1 for i := 1, 2, 3, ..., n: f := f * i return f