Increment value in twig file

I have a loop withing a .twig file that outputs elements.

I need to increment a value withing each element. I know how to do it in PHP, but an not clear how to do it withing a twig document. I can't really do it in controller. Any suggestions?

{% set myVal = 50 %}

{% for item in items%}
     {{ myVal = myVal + 10 }}
{% endfor %}

Solution 1:

Use this:

{% set myVal = 50 %}

{% for item in items %}
     {% set myVal = myVal + 10 %}
{% endfor %}

For declaring, setting values, setting blocks/forms, etc. you must use {% %}. For output, there is {{ }}

Solution 2:

Here is the better way -

{% for item in items %}
  {% set counter = ( counter | default(0) ) + 1 %}
  <p>{{ counter ~ ' ). ' ~ item.title }}</p>
{% endfor %}

See how the counter is being increased by 1.