Program control

If

If operation which expects a Compare operation to return and execute the operations if true.

import {If} from "#program-control"

Use the then or else chained methods to control the flow.

import {Bool} from "#primitives"
import {Assign, Compare} from "#basics"
import {If} from "#program-control"

const MyBool = new Bool(true)

const MyIf = new If(new Compare(MyBool, "=", true))
    .then([new Assign(MyBool, false)])
    .else([new Assign(MyBool, true)])

ForOf

A For-Of loop, increments a reference until it has reached a specified value.

import {ForOf} from "#program-control"

ForOf has 3 mandatory parameters:

• For: the variable which will be incremented
• With: the initial value of For
• To: the target value for For

Use the do chained method to add operations.

import {Int} from "#primitives"
import {Assign, Calc} from "#basics"
import {ForOf} from "#program-control"

const MyInt = new Int()

// For i := 5 to 10
const MyForOf = new ForOf(MyInt, 5, 10)
    .do([
        new Assign(MyInt, new Calc(MyInt, "+", 1))
    ])

A 4th parameter tells how the loop should be incremented.

import {Int} from "#primitives"
import {ForOf} from "#program-control"

const MyInt = new Int()

// For i := 5 to 10 By 1
const MyForOf = new ForOf(MyInt, 5, 10, 1)
    .do([])

Return

Force an immediate return.

Return do not have any parameters.

import {Return} from "#program-control"

const MyReturn = new Return()

While

A while loop, first parameter has to be a Compare operation which will break the loop once it returns true.

import {Int} from "#primitives"
import {Assign, Calc, Compare} from "#basics"
import {While} from "#program-control"

const MyInt = new Int()

// While i < 10
const MyWhile = new While(new Compare(MyInt, "<", 10))
    .do([
        new Assign(MyInt, new Calc(MyInt, "+", 1))
    ])

Loop safety

vif-sim has a loop security built-in, it does not know if the loop is infinite but will stop automatically if the loop takes longer than 100ms to execute.

Also there's a chance that the loop will trigger an integer overflow at some point and stops the program.

The following code will crash because i will reach 127 before the loop ends:

const fb = new Fb({
            interface: {
                temp: {
                    i: new SInt(6),
                }
            }, body() {
                return [
                    new While(new Compare(this.temp.i, ">", 5))
                        .do([
                            new Assign(this.temp.i, new Calc(this.temp.i, "+", 1))
                        ]),
                    new UnitTest("Unreachable", this.temp.i, "=", 5),
                ]
            }
        }
    );