Desde loop(For Loop)

Desde repeats the same code over and over again until its expression is fulfilled (is true).

Typically, the desde loop is used to navigate between items in an array or dictionary, but also to execute code that will be repetitive.

---

“Desde” loop syntax

Syntax example

desde (declaration; expresion; statement)
  #Code block
fin

Declarations	Description
Declaration	This is executed (only once) before the execution of the code
Expresion	Define the conditions for the code block to be executed
Statement	This is executed (every time) after executing the code block

Sample code

/*
In the following code
  as long as the variable i is less than or equal to 10
  the conditional from will continue to run.

 The program will print on the screen:
 0 1 2 3 4 5 6 7 8 9 10
 */

 desde (i = 0; i <= 10; i++)
   escribir(i)
 fin

/*
In this other example
the program will print on the screen:
10 9 8 7 6 5 4 3 2 1 0
*/

desde (i = 10; i >= 0; i--)
  escribir(i)
fin
#output: 10 9 8 7 6 5 4 3 2 1 0

---

A different way can be specified by changing the increment expression.

desde(i = 0; i < 50; i = i+10)
  imprimir(i)
fin
#output: 0 10 20 30 40

---

Use of libraries

Expresiones of the desde loop can implement the use of libraries, like this:

/*
This operation compare the amount
of items in the fruit array and
will write them on screen, like this:

> apple
> grape
> cherry
*/

fruit = ["apple", "grape", "cherry"]

desde(i=0; i < lista.longitud(fruit); i++)
  imprimir(fruit[i])
fin

---

Nesting “desde” loop

When a desde loop contains another desde loop within it, it’s called nested loop.

When the desde loop ( parent ) executes and reaches a nested loop ( child ), the parent loop does not continue until the child loop completes all of its cycles (until it is true). This whole cycle will repeat itself until the parent loop is true.

/*
This operation compares the quantity
of elements in the fruit array and adjectives
will write them on screen, like this:

> green apple
> green grape
> green cherry
> big apple
> big grape
> big cherry
> delicious apple
> delicious grape
> delicious cherry
*/

fruit    = ["apple", "grape", "cherry"]
adjectives = ["green", "big", "delicious"]

desde(i=0; i < lista.longitud(adjectives); i++)
  desde (e=0; e < lista.longitud(fruit); e++)
    escribir (adjectives[i].." "..fruit[e])
  fin
fin