7.2 Looping directives

Xenv provides two looping constructs: $$loop and $$range. Both allow you to repeat a block of text multiple times on the output.

The $$loop directive implements a foreach loop. The syntax is:

$$loop name args...
text
$$end

Here, args is a whitespace-delimited list of words. When the construct is scanned, args is subject to all kinds of expansions and text is scanned verbatim. During expansion, the $$loop directive will assign each value from this list to the variable name and expand text. Whatever value name has before entering the loop will be restored after leaving it.

For example, the following construct:

$$loop X A B C
This is $X
$$end

will produce the following expansion:

This is A
This is B
This is C

The $$range statement implements a for loop:

$$range name start stop [incr]
text
$$end

The three arguments are subject to expansions, whereas text is scanned verbatim. During expansion, the variable name is initialized with the value start and text is expanded. Then, the value of name is incremented by the value of incr and expansions continue until the stop value is reached (inclusive).

If incr is not given explicitely, +1 is assumed if stop > start and -1 is assumed otherwise.

For example:

$$range X 1 4
Number $X
$$end

expands to:

Number 1
Number 2
Number 3
Number 4