draft-extension-heredocs.md

title	author	date
[DRAFT] The Jevko Syntax: Heredoc Extension Specification	by Darius J Chuck	Draft: December 2022.

This draft is superseded by The Jevko Syntax: Extensions Specification.

Illustration

Details

Extends the Subjevko rule from:

Subjevko = Prefix Opener Jevko Closer

to:

Subjevko = Prefix Opener Jevko Closer / Prefix Escaper Quoter HeredocTag Quoter Heredoc Quoter HeredocTag Quoter

where:

Quoter = "'"
HeredocTag = *<any codepoint except Quoter>
Heredoc = *<any code point>

additionally:

• the second instance of HeredocTag must be identical to the first
• and Heredoc must not contain the sequence:

Quoter HeredocTag Quoter

where HeredocTag is also identical to the first HeredocTag instance.

Examples of valid heredocs

Empty Heredoc with empty HeredocTag:

some prefix `''''

---

Empty Heredoc with HeredocTag = some tag

some prefix `'some tag''some tag'

---

Nonempty Heredoc with empty HeredocTag:

some prefix `''heredoc contents which contain []`]''

in this case Heredoc = heredoc contents which contain []`].

Examples of invalid heredocs

What looks like empty Heredoc with HeredocTag = some tag, but the second instance of HeredocTag (some other tag) does not match the first:

some prefix `'some tag''some other tag'

in this case 'some other tag' would actually be considered part of the Heredoc and the second instance would be considered missing.

---

What looks like empty Heredoc with HeredocTag = some tag, but the Heredoc contains the forbidden sequence 'some tag':

some prefix `'some tag'content which contains 'some tag' and continues until here'some tag'

in this case Heredoc = content which contains rather than content which contains 'some tag' and continues until here. The remainder of the example ( and continues until here'some tag') is actually a Suffix of the parent Jevko.

Alternatively, if this example was to continue further like this:

some prefix `'some tag'content which contains 'some tag' and continues until here'some tag'
another prefix [something else]

then the remainder is actually part of the Prefix of the next Subjevko, making the Prefix:

 and continues until here'some tag'
another prefix 

rather than another prefix .