Generating reserved character sequences with EGL scripts

[YvesTLS]

How can we manage to generate reserved character sequences like "[%", "%]", "[" or "]" with EGL scripts?
I cannot fond the way to escape them, they are always interpreted as sequence of control.
The documentation tells about escaping reserved keywords, but nothing about those character sequences.

Thanks for your help

[kolovos]

There's no escaping mechanism for such sequences but as a workaround you could use string concatenation as shown below.

[%=startTag()%]"Hello world"[%=endTag()%]

[%
operation startTag() {
    return "[" + "%=";
}

operation endTag() {
    return "%" + "]";
}
%]

This will produce:

[%="Hello world"%]

On a related note, in this branch we have added support for custom tags to EGL (see these tests for examples) but I wanted to write a few more tests before merging into the main branch. Would such a feature be useful for your use case?

[YvesTLS]

Hello Kolovos,

Thanks for your reply. I tried this kind of approach already but, unfortunately, this does not work with templates.
For instance, let use it in the following EGL script:

[%
TemplateFactory.setOutputRoot('.');

var genTemplate: Template = TemplateFactory.prepare(test());
genTemplate.generate("Test.txt");

@template
operation test() {
	var x = startTag();
	var y = "***";
%]

[%=startTag()%]"Hello world"[%=endTag()%]

[%}

operation startTag() {
    return "[" + "%=";
}

operation endTag() {
    return "%" + "]";
}
%]

Then, the content produced in the Test.txt file is:
Hello world

Rather than:
[%="Hello world"%]
as expected.

The point is that the output of a template is interpreted as EGL code. So, whatever the way you build the character sequences, they would be interpreted the same way. So, an escape mechanism would be really useful, especially for those who want to "generate generators"!

[kolovos]

You could achieve this by using EGX to run your EGL-generating template, as shown here. Would this work for your use case?