range

{% for i in range(0, 3) %}
  {{ i }},
{% endfor %}

{# outputs 0, 1, 2, 3, #}

When step is given (as the third parameter), it specifies the increment (or decrement for negative values):

{% for i in range(0, 6, 2) %}
  {{ i }},
{% endfor %}

{# outputs 0, 2, 4, 6, #}

Note that if the start is greater than the end, range assumes a step of -1:

{% for i in range(3, 0) %}
  {{ i }},
{% endfor %}

{# outputs 3, 2, 1, 0, #}

The Canvas built-in .. operator is just syntactic sugar for the range function (with a step of 1, or -1 if the start is greater than the end):

{% for i in 0..3 %}
  {{ i }},
{% endfor %}

Arguments