Control structures

Control structures refer to the decisions made that affect the order of execution of the code. Although F# is an expression-based language, it also provides control flow constructs common of statement-based languages, such as looping, that allows us to write code with side-effects. We will be discussing this, as well as how to express conditions, in the following sections.

Looping

There are two types of loops: the for loop and the while loop. The For loops have the following two types of expression:

• for...to: This iterates over a range of values
• for...in: This is more like the foreach loop in other .NET languages as it loops over an enumerable collection

The for...to expression

The for...to expression loops/iterates over a range of values. The range can be forward/reverse or generated via a function. The return of this expression is unit type.

The forward expression works by incrementing the following values in the loop:

// A simple for...to loop.  
let function1() = 
   for...