Two for-loop variants are supported: a C-style counting for loop
consisting of an initialization expression, a test condition
and a step expression and a for-in-loop variant which allows
enumerating properties of objects or items of arrays.

Additionally, utpl supports an alternative syntax suitable for
template block tags.


-- Expect stdout --
A simple counting for-loop:
Iteration 0
Iteration 1
Iteration 2
Iteration 3
Iteration 4
Iteration 5
Iteration 6
Iteration 7
Iteration 8
Iteration 9


If the loop body consists of only one statement, the curly braces
may be omitted:
Iteration 0
Iteration 1
Iteration 2
Iteration 3
Iteration 4
Iteration 5
Iteration 6
Iteration 7
Iteration 8
Iteration 9


Any of the init-, test- and increment expressions may be omitted.

Loop without initialization statement:
Iteration null
Iteration 1
Iteration 2


Loop without test statement:
Iteration 0
Iteration 1
Iteration 2


Loop without init-, test- or increment statement:
Iteration 1
Iteration 2
Iteration 3


For-in loop enumerating object properties:
Key: foo
Key: bar


For-in loop enumerating array items:
Item: one
Item: two
Item: three


A counting for-loop using the alternative syntax:
Iteration 0
Iteration 1
Iteration 2
Iteration 3
Iteration 4
Iteration 5
Iteration 6
Iteration 7
Iteration 8
Iteration 9


A for-in loop using the alternative syntax:
Item 123
Item 456
Item 789

-- End --

-- Testcase --
A simple counting for-loop:
{%
	for (i = 0; i < 10; i++) {
		print("Iteration ");
		print(i);
		print("\n");
	}
%}

If the loop body consists of only one statement, the curly braces
may be omitted:
{%
 	for (i = 0; i < 10; i++)
		print("Iteration ", i, "\n");
%}

Any of the init-, test- and increment expressions may be omitted.

Loop without initialization statement:
{%
	for (; j < 3; j++)
		print("Iteration " + j + "\n");
%}

Loop without test statement:
{%
	for (j = 0;; j++) {
		if (j == 3)
			break;

		print("Iteration ", j, "\n");
	}
%}

Loop without init-, test- or increment statement:
{%
	for (;;) {
		if (k++ == 3)
			break;

		print("Iteration ", k, "\n");
	}
%}

For-in loop enumerating object properties:
{%
	obj = { foo: true, bar: false };
	for (key in obj)
		print("Key: ", key, "\n");
%}

For-in loop enumerating array items:
{%
	arr = [ "one", "two", "three" ];
	for (item in arr)
		print("Item: ", item, "\n");
%}

A counting for-loop using the alternative syntax:
{% for (x = 0; x < 10; x++): -%}
Iteration {{ x }}
{% endfor %}

A for-in loop using the alternative syntax:
{% for (n in [123, 456, 789]): -%}
Item {{ n }}
{% endfor %}
-- End --