Page Template Language -- help with the grammar !

Folks:

I'm trying to write a server side page templating thingy.

Here's what I would like to do, syntax wise:

[[....]] are code sections.
Code sections are copied to the resulting document verbatim.
If code sections appear within quoted strings, they are
ignored.

[.....] are expression sections. They are converted
into:

      out.println(.....)

everywhere they occur in the source (even within quoted
strings).

\[[ escapes the code section. \[[ prevents a code section
from starting and is copied to the resulting document as "[["

\[ escapes the expression section. \[ does not start a
expression section and is copied to the resulting document
as "["

Everything else is html text and is copied to the resulting
document verbatim.

For example:

================ Source ======================
<foo value="[fillin]">bar</foo>

"
some quoted text [[ code section ignored in string ]]
[expression-filledin-string]
"

[[ ...code ]]

\[[ foo ]]
\[ foo ]

===================== Result ========================
<foo value="out.print(fillin)">bar</foo>

"some quoted text [[ -- totally ignored ]]
out.print(filledin2)
"

...code....

[[
foo
]]

[ foo ]
====================================================

Trying to write a grammar/lexer for this is proving
to a be a bit tricky. This is because:

a) [ and [[ have a common prefix "["
b) \[ and \[[ are both valid escape sequences. However,
if I have:

\[[text]]

I want to ignore the entire line, not treat that as:

--> \[ [text] ] --> \[ out.print(text) ]

So far I've come up with:

text -> html* | exp* | code*
html -> all chars
exp -> '[' exptext ']'
code -> '[[' codetext ']]'
codetext -> (any char)*
exptext -> (any char)*

But I want to specify that \[ does not start an exp
and \[[ does not start code. How to do that in the grammar ?

I also want to specify that \] does not end an exp
and \]] does not end code. How to do that in the grammar ?

Best regards,
--j
[How come you want to reinvent php rather than using the one that
already exists? -John]

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