TABLE OF CONTENTS
(Make a search on the tag in the right column to jump
to the associated section.
Vim users can simply type * on the tag;
Emacs users do that with C-s C-w (I think);
Other editors: I don't know!)
===========================================================
Introduction intro_tag
Input files input_tag
Paragraphs paragraphs_tag
Declaring patterns patterns_tag
Classes classes_tag
Protecting input protect_tag
Technical stuff technical_tag
An example: i-doc.lua example_tag
The Gates in Interpreter gates_tag
The interpreter table interpreter_tag
The interpreter.core.tools table interpreter_tools_tag
The interpreter.core.reader table interpreter_reader_tag
===========================================================
================================== intro_tag
=== Introduction =================
==================================
Interpreter preprocesses input files before their contents is fed to TeX. It
is meant to write document with whatever markup one wishes to define while
using normal TeX macros in the background. As a simple example, suppose you
have a macro "\bold" to put text in boldface; then Interpreter lets you map
"*text*", or "<strong>text</strong>", or simply "!text", or anything else, to
"\bold{text}". Interpreter doesn't perform any trickery with active
characters; instead, it manipulates the strings representing the lines of
a file and search for patterns.
There are two main advantages: first, TeX documents can be typeset with
a completely non-TeX syntax; second, if one uses some lightweight markup
language, the source file is much easier to read and might even be more useful
than the typeset PDF file, e.g. for some technical documentation you want to
read directly in your text editor while writing code (powerful editors
generally have their own documentation in such a format, for a good reason).
A third advantage, not explored in this documentation, is that while feeding
modified lines to TeX you can also translate the original lines into, say,
HTML, and write them to an external file, thus creating both PDF and HTML
output at once.
Interpreter has been rewritten with the Gates package (actually, only
the Lua side) in version 1.1. That hasn't changed anything to its default
behavior, but now it can also be customized quite deeply, since its
code is a collection of small chunks with names that can be externally
controlled and/or augmented. See the Gates documentation for further
information. The last sections of this documentation describe the gates
in Interpreter.
================================== input_tag
=== Input files ==================
==================================
Once Interpreter is loaded with
\input interpreter
in plain TeX or
\usepackage{interpreter}
in LaTeX, files to be processed are input as follows:
\interpretfile{<language>}{<file>}
There should exist a file "i-<language>.lua" containing the language used in
<file>. For instance, the source of this documentation is
"interpreter-doc.txt", input in the master file "interpreter-doc.tex" with
\interpretfile{doc}{interpreter-doc.txt}
and the interpretation to be used is defined in "i-doc.lua". The contents of
such an interpretation file is the object of the rest of this documentation.
================================== paragraphs_tag
=== Paragraphs ===================
==================================
Interpreter doesn't process lines one by one. Instead, it gathers an entire
paragraph and then processes the lines. It is important because you can
manipulate an entire paragraph when a given pattern is detected, and modify
several lines according to what happens in only one. A paragraph in
Interpreter has nothing to do with what TeX considers a paragraph; instead, it
is defined by the following string.
> interpreter.paragraph [Default: blank line with spaces ignored]
A string to be interpreted as a paragraph boundary when Interpreter collects
lines before processing them. The string actually represents a pattern, so
magic characters are obeyed. The default is "%s*", i.e. a blank line is
considered a paragraph boundary, spaces notwithstanding. Of course, the end
of the file itself is a paragraph boundary.
================================== patterns_tag
=== Declaring patterns ===========
==================================
Once the lines of a paragraph have been collected, Interpreter searches them
trying to match declared patterns, but it doesn't do so indiscriminately:
patterns are searched in a given order, as explained below.
Patterns are searched for in each line only, i.e. no match can occur across
lines. However, since you can manipulate entire paragraphs based on a match in
one line, the limitation easily vanishes.
> interpreter.add_pattern(<table>)
This is the basic function used to defined patterns. The <table> may
contain the following entries, along other entries Interpreter won't use
but which can be useful to you, especially with "call" below. The function
returns a table.
>> class [Default: "intepreter.default_class"]
The class of the pattern. See the section on classes.
>> pattern
The pattern to match. Lua's magic characters are in force and should be
escaped with "%" if necessary, unless "nomagic" is "true" (or the pattern
itself is the result of "interpreter.nomagic").
>> nomagic [Default: "false"]
A boolean deciding whether the pattern should be transformed with
"interpreter.nomagic".
>> replace
The replacement for the pattern, applied only if there is no "call" entry.
This may be a string, a table or a function. Interpreter simply executes
something similar to "string.gsub()", hence the replacement follows this
function's ordinary syntax. More precisely, if "replace" is a string, the
pattern is replaced with it; in this string, "%n" may be used to denote the
_n_th capture in the pattern. If "replace" is a table, the first capture or
the entire match (if there is no capture) is used as the key, and the
associated value is used as the replacement. If "replace" is a function, it
is called with the captures passed as arguments, or the entire match if
there is no capture. For instance, the following pattern will replace all
"*text*" with "\bold{text}":
interpreter.add_pattern{
pattern = "%*(.-)%*",
replace = [[\bold{%1}]]
}
>> offset [Default: 0]
The number of positions Interpreter should shift to the right after a match
has occurred. Normally, Interpreter starts searching for another occurrence
of the current pattern at the same position where it found the last one.
However, loops might easily occur: the replacement for a pattern may very
well contain another match for the same pattern, so Interpreter will get
stuck. Suppose for instance you want to replace "TeX" with "\TeX". The
first match will do that, but then Interpreter will start searching again
at the backslash, producing "\\TeX", then "\\\TeX", etc. In this case, if
you set "offset" to 2 in the pattern, then search will start again at the
"e" and no new match will occur.
>> call
This entry shall contain a function to be called if there is a match (if
this entry exists, "replace" isn't applied). It is meant to perform complex
tasks that aren't amenable to simple string replacement. The function will
be executed as follows:
function (paragraph, line, index, pattern)
"paragraph" is a table representing the current paragraph; lines are stored
at successive indices. The last line of this paragraph is always the
paragraph boundary (see "interpreter.paragraph"), unless the paragraph
stopped at the end of the file. The second argument, "line", is a number
representing the index in "paragraph" containing the line where the pattern
was found; "index" is the position in this line where the match occurred.
Finally, "pattern" is the entire table declared with
"interpreter.add_pattern" and containing all the entries discussed here.
The function may return zero, one, or two numbers. If it returns none, the
search for the next occurrence of the pattern will start again on the same
line (rather, on the line with the same position in the paragraph), at
"index". If it returns one number, the search will resume at the same line
but at position _n_, with _n_ the returned number. Finally, if two numbers
are returned, the search will resume at line _m_ at position _n_, _m_ and
_n_ being the returned values. Specifying which line should be examined
when the search resumes might be necessary if the function adds new lines
in the paragraph _before_ the current line, since Interpreter only keeps
count of line numbers.
The entire paragraph can thus be modified if necessary. For instance,
suppose you want to declare comments in your source file with only
"!Comment" in the first line, i.e. TeX should ignore a paragraph such as:
!Comment
This should be ignored
by TeX
Then the following pattern will do (where the function requires only the
first argument):
local function comment (paragraph)
for n, l in ipairs(paragraph) do
paragraph[n] = "%" .. l
end
end
interpreter.add_pattern{
pattern = "^!Comment",
call = comment
}
> interpreter.nomagic (string)
A function which reverses the usual Lua magic for patterns: ordinary magic
characters are normal characters here, unless they are prefixed with "%", in
which case they are magic again. For instance, a pattern like ".+" is
normally interpreted as ``one or more characters''. If passed to this
function, a pattern is returned meaning ``a dot followed by a plus sign''.
On the contrary, "%.%+" normally has the second interpretation, while with
"interpreter.nomagic" it has the first one. The function makes another
transformation: "..." is used to denote a capture "(.-)". Thus
"interpreter.nomagic('*...*')" returns a pattern matching any number of
characters surrounded by stars and capturing those characters; this would be
expressed in ordinary Lua magic as "%*(.-)%*".
================================== classes_tag
=== Classes ======================
==================================
As already alluded to, the search for patterns isn't done at random. Instead,
patterns are organized in classes, which are applied one after the other. More
precisely, the process is as follows: Interpreter searches the entire
paragraph for the first pattern in class~1, then for the second pattern in the
same class, then for the third, etc., then when there is no pattern left in
class~1 it does the same with class~2, up to class~_n_, where _n_ is the
highest class number such that there exists a class _n - 1_ (in other words,
classes should be numbered consecutively). Finally, the same goes for the
patterns in class~0 (which always exists, even if it contains no pattern).
Inside a class, patterns are ordered by length from long to short, or
alphabetically if two patterns have the same length. This means that if you
use e.g. "/text/" for italics and "//text//" for bold, you don't need to put
the second pattern in a class before the first to avoid "//text//" being
interpreted as two empty arguments in italics surrounding a text in roman.
Since the way the bold-pattern will be declared, e.g. "//(.-)//", is probably
longer than for the italic-pattern, e.g. "/(.-)/", it will always match first.
That said, the sorting isn't very clever and simply relies on the number of
symbols, no matter what they mean; in the patterns above, the parentheses
denote a capture but they still count in the pattern's length as understood by
Interpreter. Alternatively, while ".*" denotes ``zero or more character'' and
"%+" means ``a plus sign'' ("+" being magic, you have to escape it to refer to
it), in Interpreter's eye the two patterns have the same length: two. Finally,
one should be aware that patterns declared with a "nomagic" entry set to
"true" are sorted after they've been transformed (so that their real length
might not be obvious). So classes are needed when patterns need a proper
ordering no matter their lengths. For instance, some patterns should always be
declared first, as they protect input from Interpreter (see next section),
while others might need to be declared last, as they rely on what previous
patterns might have done. Besides, classes are metatables for the patterns
they contain.
> interpreter.default_class [Default: 1]
All patterns belong to a class, even though you may omit the "class" entry
when declaring one. In this case, the pattern is assigned to the class
denoted by this number.
> interpreter.set_class(number, table)
Defines class "number" as "table". Classes don't need to be defined
beforehand for patterns to be added to them (rather, Interpreter defines
them implicitly when needed). However, classes are also metatables for the
patterns, so that if there lacks an entry in a pattern's table, the class's
entry is used if it exists. The function returns a table.
================================== protect_tag
=== Protecting input =============
==================================
Sometimes you want Interpreter to refrain from interpreting; that is most
useful for verbatim code, for instance. There are various ways to do that.
> interpreter.active [Default: true]
A boolean switching Interpreter on and off. Beware, the switching applies
only starting at the next paragraph.
> interpreter.protect([line])
A function protecting all or part of the current paragraph. If "line" is
given, it should be a number _n_, and line _n_ in the current paragraph will
be protected; without "line", the entire paragraph is protected. Protecting
means that the patterns not yet searched for will be ignored. For instance,
if you want material to be read verbatim when surrounded with "<code>" and
"</code>", you can declare a pattern as follows:
local function verbatim (buffer)
buffer[1] = "\\verbatim"
buffer[#buffer - 1] = "\\endverbatim"
intepreter.protect()
end
interpreter.add_pattern{
pattern = "^%s*<code>%*s$",
call = verbatim,
class = 1
}
This code is extremely simplified : it assumes that "<code>" and "</code>"
starts and ends the paragraph and that "</code>" isn't the last line of the
file (otherwise it'd also be the last line in the paragraph, whereas here
the last one is the paragraph boundary). An important point is that the
pattern belongs to the first class, so it is called before all other
patterns (provided there is no shorter pattern in class~1) and prevents them
from doing anything, since the entire paragraph is protected. (Typesetting
the material as verbatim material obviously depends on the "\verbatim"
macro, not on Interpreter.)
> interpreter.escape
A character which prevents patterns from being replaced if immediately
preceded by it. As an example, if "interpreter.escape = '_'", and "*text*"
denotes italic, then "*text*" will produce _text_ while "_*text*" will
produce *text*. Once a paragraph has been processed, Interpreter removes all
escape characters. Only one character can be an escape character.
> interpreter.protector(left[, right]) ["right" defaults to "left"]
Defines two characters to protect what they surround. In other words,
Interpreter replaces patterns only if the match isn't found between "left"
and "right". Unlike the escape character, you can define as many protectors
as you wish; and unlike the escape character again, Interpreter _doesn't_
remove them once the paragraph has been processed, so you must take care of
them. For instance:
intepreter.protector('"')
interpreter.add_pattern{
pattern = '"(.-)"',
replace = '\\verb`%1`',
class = 0
}
Anything between double quotes will be left untouched; then, when the
paragraph has been processed for all other classes, a pattern in class~0
calls the "\verb" command to take care of the argument. Note that the
protectors should enclose what they protect without coinciding with it; this
is not the case here, which is why the pattern is applied.
> interpreter.direct [Default: two percent signs then "I" and at least one space]
A string, actually a pattern, signalling that the line which it begins
should be processed as Lua code. The default is "%%%%I%s+", i.e. "%%I"
followed by at least one space. The pattern shouldn't declare itself as
attached to the beginning of the line (as in "^%%%%I%s+") because they will
be matched at the beginning of the line only anyway. The line is processed
with the "loadstring" function, and then turned into an empty line. For
instance:
%%I interpreter.active = false
This won't be interpreted...
%%I interpreter.active = true
As this example shows, lines flagged with "interpreter.direct" don't obey
"interpreter.active" and are always processed as described above.
================================== technical_tag
=== Technical stuff ==============
==================================
You don't have to bother with this section if you don't mind how Interpreter
does its job; actually you won't learn much anyway.
> interpreter.reset()
A function which resets everything to default and deletes classes. It is used
when calling "\interpretefile" so that new interpretetions start from zero.
> interpreter.register(function)
A function called to put Interpreter's main function into the
"post_linebreak_filter" callback; you can redefine it at will. If it is
undefined, "callback.register()" is used, unless "luatexbase.add_to_callback()"
is detected. (The detection takes place at the first call to
"\interpretfile", so there is no need to load Interpreter after
"luatexbase".)
> interpreter.unregister(function)
A function called to remove Interpreter's main function from the
"post_linebreak_filter" callback. It works similarly to the previous one.
================================== example_tag
=== An example: i-doc.lua ========
==================================
\interpretfile{doc}{i-doc.lua}
================================== gates_tag
=== The Gates in Interpreter =====
==================================
Interpreter is written with the Gates package (only the Lua side,
actually). It means that it can be hacked down to the core. Here I'll
simply list the gates involved; you should read the Gates
documentation to learn how to use them.
There are three gates families: "interpreter", associated with the main
"interpreter" table, contains the user interface; "interpreter_tools",
associated with "interpreter.core.tools" table, contains internal
functions; finally "interpreter_reader", associated with the
"interpreter.core.reader" table, contains the main functions used to
read the file.
Whenever I mention a conditional or a loop, I mean the local conditionals
and loops, relative to the l-gate where the gate appears. Also, the
syntax indicates the arguments a gate uses, not all the arguments that
are passed to it (which are simply what the previous gate has returned).
As an example of customizing Interpreter with Gates, you could very
well add a bit of code which does something to all lines. Inserting a
small gate, say "everyline", after "check_direct" in "aggregate_lines"
below would do the trick, e.g.:
function interpreter.core.reader.everyline (file, line)
line = dosomething(line)
return file, line
end
interpreter.core.reader.add(
"everyline", "aggregate_lines", "after check_direct")
interpreter.core.reader.conditional(
"everyline", "aggregate_lines", function (f, l) return l end)
(Note that it is important to check that the line really exist,
because one might have hit the end of the file; hence the conditional,
as with others gates in "aggregate_lines").
================================== interpreter_tag
=== The "interpreter" table ========
==================================
All the user functions in "interpreter" are simple m-gates, so they can
be treated as ordinary functions, except "interpreter.add_pattern",
which is an l-gate containing, built as:
add_pattern
. ensure_class
. apply_nomagic
. insert-pattern
. . do_insert
. . sort_class
> ensure_class (<pattern>) [m-gate]
Creates the class of <pattern> if necessary, and set it as the metatable
for <pattern>. Classes themselves are kept in the "interpreter.core.classes"
table. The gate return <pattern> and the class number.
> apply_nomagic (<pattern>, <class>) [m-gate]
Transforms the "pattern" entry in <pattern> with "intepreter.nomagic";
tied to a conditional that returns <pattern>'s "nomagic" entry (so
the gate is executed only if "nomagic" is true); autoreturns both
arguments.
> insert_pattern (<pattern>, <class>) [l-gate]
An autoreturning l-gate containing the following two gates.
> do_insert (<pattern>, <class>) [m-gate]
Adds <pattern> to <class> (i.e. "interpreter.core.classes[<class>]").
> sort_class (<pattern>, <class>) [m-gate]
Sorts <class> with function "interpreter.core.tools.sort". This gate
can be skipped to apply the patterns in the order in which they were
declared.
============================================= interpreter_tools_tag
=== The interpreter.core.tools table ========
=============================================
All the functions in the "interpreter.core.tools" all are simple m-gates.
> sort (<patt1>, <patt2>) [m-gate]
Returns true if the pattern in "patt1" is longer than the one in
"patt2", or if they have the same length and the first ranks before
the second with respect to alphabetical order. The gate is used in
the "interpreter.sort_class" m-gate.
> xsub (<string>, <index>, <pattern>, <replacement>) [m-gate]
Returns <string> with <pattern> replaced with <replacement>, but only
once, and only after <index>.
> protector (<string>, <index>) [m-gate]
Checks whether <index> in <string> isn't between characters declared
with "interpreter.protector". If that is the case, the function returns
"nil" and the index of the second protector. Otherwise, it returns
<index>.
> get_index (<string>, <pattern>, <index>) [m-gate]
Checks whether <pattern> occurs in <string>, starting at <index>. If
it does, but if <index>-1 is "interpreter.escape", calls itself with
<index>+1. Otherwise, calls "interpreter.core.tools.protector" to
check whether <index> is in a protected part of the string. If so,
calls itself with <right>+1 instead of <index>, where <right> is the
second return value of of "interpreter.core.tools.protector", i.e.
it searches again after the right protector. If <index> is found,
end of story, returns <index>, otherwise returns nothing.
The "interpreter.core.tools" table also contains
"magic_characters", a table with an entry for each magic character in Lua except
`"."' and `"%"'; the values to those entries are the same characters
prefixed with `"%"'. The table is used by "interpreter.nomagic" to spot
and replace magic characters, with the dot and the percent sign dealt
with independantly.
============================================= interpreter_reader_tag
=== The interpreter.core.reader table =======
=============================================
Interpreter works by hooking in the "open_read_file" callback; the
function registered there is the "interpreter.core.reader.input"
l-gate, built as follows:
input
. unregister
. . set_unregister
. . use_unregister
. open_file
. set_reader
> unregister (<filename>) [l-gate]
Contains the following two m-gates; <filename> is received from
"input", which itself receives it from the callback, i.e. that's the
file that's being input (the second argument to "\interpretfile").
It is also automatically returned.
> set_unregister () [m-gate]
Sets the function to remove "input" from the callback, namely
"interpreter.unregister"; the gate is called only if gate
"interpreter.unregister" doesn't already exits. If "luatexbase" is
detected, the functions there are used; otherwise, "callback.register"
is used with "nil" as the second argument.
> use_unregister () [m-gate]
Calls "interpreter.unregister()". (You don't want the next input file
to be processed with Interpreter by default, that's why you remove
the callback function; not that the current one is nonetheless
processed with the current file, of course.)
> open_file (<filename>) [m-gate]
Returns "io.open(<filename>)".
> set_reader (<file>) [m-gate]
Returns a table with a "reader" entry containing a function whose
definition is
function ()
return interpreter.core.reader.read_file(f)
end
That's the convention for the "open_read_file" callback: it should
return such a table, and the function will be called each time a
line is required from the input file.
So most of the work is done by "interpreter.core.reader.read_file",
which is why it is so heavy; it receives a file handle:
read_file
. make_paragraph
. . aggregate_lines
. . . read_line
. . . check_direct
. . . insert_line
. . apply_classes
. . . pass_class
. . . . pass_pattern
. . . . . process_lines
. . . . . . switch
. . . . . . call
. . . . . . replace
. . . . . . protect
. . . unprotect
. . . . undo_protected
. . . . unprotect_lines
. . . remove_escape
. return_line
> make_paragraph (<file>) [l-gate]
The big l-gate that contains everything that follows, barring
"return_line". It is called if and only if the "interpreter.core.lines"
table is empty; that table is where lines of a paragraph are stored,
and it is emptied by "return_line".
> aggregate_lines (<file>, <line>) [l-gate]
The main l-gate that reads line from <file> and stores them in
"interpreter.core.lines". It loops until <line> is "nil" or equivalent
to "interpreter.paragraph". (Of course, <line> is "nil" on the first
iteration, but the "loopuntil" conditional is evaluated after that
first iteration, during which the last subgate "insert_line" will
probably returns a line.)
> read_line (<file>) [m-gate]
Reads the next line from <file>, and returns <file> and that line.
> check_direct (<file>, <line>) [m-gate]
If <line> begins with "interpreter.direct", removes it and use
"loadstring" on the resulting string. Returns <file> and <line>, the
latter set to an empty string is the previous operation applied. The
gate depends on a conditional: <line> should be non-"nil" (of
course), and "interpreter.direct" should be defined.
> insert_line (<file>, <line>) [m-gate]
Adds <line> to "interpreter.core.lines". Automatically returns the
two arguments (and if <line> isn't "nil" or equivalent to
"interpreter.paragraph", it will be executed again).
> apply_classes () [l-gate]
The l-gate that applies transformations to the lines, once the paragraph
has been gathered, with the gates that follow. For each class, it
will apply each pattern on each line. It depends on a conditional:
"interpreter.core.lines" shouldn't be empty, and "interpreter.active"
should be true.
> pass_class () [l-gate]
This gate iterates on all classes in "interpreter.core.classes" and
then on class 0. On each iteration it checks beforehand whether the
paragraph is protected, i.e. "interpreter.core.reader.protected" isn't
a boolean (see "unprotecte" below). On each iteration, the class
number and the class itself are returned. (This behavior is
implemented with a Gates iterator.)
> pass_pattern (<ignored>, <class>) [l-gate]
Same as "pass_class", except it iterates on the patterns in "class":
it is executed as long as "interpreter.core.reader.protected" and
returns the patter number and the pattern itself. (The <ignored>
argument isn't used; it is for the "pass_class" iterator; the same
holds for the following gates.)
> process_lines (<ignored>, <pattern>) [l-gate]
Again, this calls an iterator. It browses each line in "interpreter.core.lines"
and returns the line's number (provided it is valid, i.e. not a table,
see "protect" below), <pattern> and the current index in that line.
To keep track of the current line and index, two internal numbers are
used: "interpreter.core.reader.current_line" and
"interpreter.core.reader.current_index".
> switch (<line>, <pattern>, <index>) [m-gate]
If <pattern> has a "call" entry, it sets the "call" gate below to
"ajar"; otherwise, if <pattern> has a "replace" entry, it sets the
"replace" gate to "ajar".
> call (<line>, <pattern>, <index>) [m-gate]
This gate is closed by default and set to "ajar" by "switch" above.
If, starting at <index>, the <pattern>'s "pattern" entry can be
found in <line> with "interpreter.core.tools.get_index" (which makes
sure that protectors are obeyed and returns <newindex>, where the
pattern is found if it occurs), the <pattern>'s "call" entry is
applied as
<pattern>.call(interpreter.core.lines,
<line>, <newindex>, <pattern>)
This may returned zero, one or two values. If nothing is returned,
"interpreter.core.reader.current_index" is set to 0, which makes
the "process_lines" iterator consider the next line. If one value is
returned, it is the new current index and "process_lines" will not
update the line number. If two values are returned, the first is the
new current line number and the second the new current index.
> replace (<line>, <pattern>, <index>) [m-gate]
This gate is closed by default and set to "ajar" by "switch" above.
This tries to find the <pattern>'s "pattern" like "call" above, and if
it is found, it applies "interpreter.core.tools.xsub" as:
xsub (interpreter.core.lines[<line>],
<newindex>, <pattern>.pattern, <pattern>.replace)
where <newindex> is defined as in "call". The return value of "xsub"
is assigned to "interpreter.core.lines[<line>]", and the current
index is set to <index> plus the <pattern>'s "offset" if any. If the
pattern wasn't found, the current index is set to 0, which makes
"process_lines" turn to the next line as explained in "call".
> protect () [m-gate]
The "interpreter.protect()" function can either protect the whole
paragraph (when no argument is passed) or a single line (when a number
is passed). In the first case, "interpreter.core.tools.protected"
takes the value "true", which is checked in various gates above. In
the second case, "interpreter.core.tools.protected" is a table with
each index indicating a line to be protected. This gate implements
the protection in that case: it iterates on all entries in the table
with "pairs" and protects the line with the same index in
"interpreter.core.lines" by transforming it into a table (with a
single entry, the string representing the original line); the type
of the line is checked in the "process_lines" iterator above. The
gate's iterator doesn't take arguments, but the function itself is
defined as taking a number (the line).
> unprotect () [l-gate]
Now all the patterns in all the classes have been applied to the
entire paragraph, and protection must be removed. This l-gate
contains the following two gates.
> undo_protected () [m-gate]
Simply sets "interpreter.core.tools.protected" to "nil" so it is
ready for the next paragraph.
> unprotect_lines () [m-gate]
Restores all the lines in "interpreter.core.lines" as simple strings.
The gate uses an iterator that simply runs "ipairs" on "interpreter.core.lines",
so the function's definition actually takes the line's number and
the line itself as arguments.
> remove_escape () [m-gate]
If "interpreter.escape" is defined, removes all its occurrences in
each line of the paragraph.
This is the end of the big "make_paragraph" l-gate. It won't be called
again until the paragraph has been fully passed to TeX, i.e. when
"interpreter.core.lines" is empty.
> return_line () [m-gate]
Pops the first line from "interpreter.core.lines" and returns it.
Since this is the very last subgate of "read_file", the line is
passed to TeX.
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