how to generate multi-line comment - stringtemplate

Question

In stringtemplate-4, how to generate a multi-line comment? For example, the template is like this (the comment's start and end are in some other template):
test(DESCRIPTION) ::= <<
*
* <DESCRIPTION>
*
>>
And DESCRIPTION is a long string, and may also contain line-feeds in it, like:
"This is a small description of the program, with a line-width of 50 chars max, so the line is split.\nFinal line."
So we want the output string like:
*
* This is a small description of the program,
* with a line-width of 50 chars max, so the
* line is split.
* Final line.
*

Answer 1

It looks like you're wanting to do a couple of things here- put the description on a line which starts
with an asterisk, but if there's a linefeed or the length is greater than 50, put that on
a separate line.
First off, I'd split the description up in the view model prior to passing it to the template, based on line feeds and the length.
I'd then make a small change to the template to separate each item in the array with
a newline and an asterisk.
Here's the group file test.stg:
group test;
description(lines) ::= <<
*
* <lines; separator="\n* ">
*
>>
I'm not sure which language you're using in the view model, but here's some Java:
public static void main(String[] args) {
STGroup templates = new STGroupFile("test.stg");
String description = "This is a small description of the program, with a line-width of 50 chars max, so the line is split.\nFinal line.";
// we add two characters at the start of each line "* " so lines can now
// be only 48 chars in length
description = addLinebreaks(description, 48);
String lines[] = description.split("\\r?\\n");
ST descTemplate = templates.getInstanceOf("description");
for (String line : lines)
{
descTemplate.add("lines", line);
}
System.out.println(descTemplate.render());
}
// used to add line breaks if the length is greater than 50
// From this SO question: http://stackoverflow.com/questions/7528045/large-string-split-into-lines-with-maximum-length-in-java
public static String addLinebreaks(String input, int maxLineLength) {
StringTokenizer tok = new StringTokenizer(input, " ");
StringBuilder output = new StringBuilder(input.length());
int lineLen = 0;
while (tok.hasMoreTokens()) {
String word = tok.nextToken()+" ";
if (lineLen + word.length() > maxLineLength) {
output.append("\n");
lineLen = 0;
}
output.append(word);
lineLen += word.length();
}
return output.toString();
}
The output I got was:
*
* This is a small description of the program,
* with a line-width of 50 chars max, so the line
* is split.
* Final line.
*
which looks slightly different to your example, but does meet the 50 char limit. I guess you can play around with it until it matches your requirements.