Kermeta provides a block notion to manage scope of variable. Instruction of the block have to be inserted between do and end keywords. Theses two keywords may be omitted for the conditional and for the loop structures.

A variable could only be accessed in the block where it was defined and in its sub blocks:

do
    var v1 : Integer init 3
    var v2 : Integer init 2
    do
        var v3 : Integer
        v3 := v1 + v2

        var v2 : Integer // error : v2 is already declared in the upper block
    end
    var v4 : Integer init v3 // error : v3 is unknown here
end

Kermeta's conditional statement is composed of at least two elements : a boolean expression and a block that is executed if the boolean is evaluated to true . You can add a third element, with the else keyword, that is executed if the boolean expression is evaluated to false .

Example 1 : if..then..else block

var v1 : Integer init 2
var v2 : String init "blah"

if v1 > 5 then v1 := v1-5

if v1 == 2 then
    v2 := v1
    v1 := v2 + v1
else
    v1 := 0
end

The if statement is an expression (see Chapter 3, Kermeta Metamodel ). As any expression in Kermeta, it can return a value. The return type of the if statement must be a super type of the values "returned" by both then and else blocks (otherwise the type checker will send an error). The values considered as the result of the evaluation (the "returned" values) of the if statement are the last evaluated statement inside then or else block

Example 2 : conditional is an expression

var s : String
    s := if false then "a" else "b" end

Example 3: a more complex conditional

var x : String
    var y : Integer init 5 
    x := if y < 3 then 
         stdio.writeln("hello")
         "a" 
         else 
         "b"
         "c" 
         end // The String "c" will be the value of x

Here is a sample of a typical loop in Kermeta.

var v1 : Integer init 3
var v2 : Integer init 6

from var i : Integer init 0
until i == 10
loop
    i := i + 1
end

See Section 2.15, “ Collections ” for functions offering iterator-like scanning.