# E.3 LaTeXML::Core::Gullet

Expands expandable tokens and parses common token sequences.

## Description

A LaTeXML::Core::Gullet reads tokens (LaTeXML::Core::Token) from a LaTeXML::Core::Mouth. It is responsible for expanding macros and expandable control sequences, if the current definition associated with the token in the LaTeXML::Core::State is an LaTeXML::Core::Definition::Expandable definition. The LaTeXML::Core::Gullet also provides a variety of methods for reading various types of input such as arguments, optional arguments, as well as for parsing LaTeXML::Common::Number, LaTeXML::Common::Dimension, etc, according to TeX’s rules.

### Managing Input

$gullet->openMouth($mouth, $noautoclose); Is this public? Prepares to read tokens from$mouth. If $noautoclose is true, the Mouth will not be automatically closed when it is exhausted.$gullet->closeMouth;

Is this public? Finishes reading from the current mouth, and reverts to the one in effect before the last openMouth.

$gullet->flush; Is this public? Clears all inputs.$gullet->getLocator;

Returns a string describing the current location in the input stream.

### Low-level methods

$tokens =$gullet->expandTokens($tokens); Return the LaTeXML::Core::Tokens resulting from expanding all the tokens in$tokens. This is actually only used in a few circumstances where the arguments to an expandable need explicit expansion; usually expansion happens at the right time.

@tokens = $gullet->neutralizeTokens(@tokens); Another unusual method: Used for things like $\backslash$edef and token registers, to inhibit further expansion of control sequences and proper spawning of register tokens.$token = $gullet->readToken; Return the next token from the input source, or undef if there is no more input.$token = $gullet->readXToken($toplevel,$commentsok); Return the next unexpandable token from the input source, or undef if there is no more input. If the next token is expandable, it is expanded, and its expansion is reinserted into the input. If$commentsok, a comment read or pending will be returned.

$gullet->unread(@tokens); Push the @tokens back into the input stream to be re-read. ### Mid-level methods$token = $gullet->readNonSpace; Read and return the next non-space token from the input after discarding any spaces.$gullet->skipSpaces;

Skip the next spaces from the input.

$gullet->skip1Space; Skip the next token from the input if it is a space.$tokens = $gullet->readBalanced; Read a sequence of tokens from the input until the balancing ’}’ (assuming the ’{’ has already been read). Returns a LaTeXML::Core::Tokens.$boole = $gullet->ifNext($token);

Returns true if the next token in the input matches $token; the possibly matching token remains in the input.$tokens = $gullet->readMatch(@choices); Read and return whichever of @choices matches the input, or undef if none do. Each of the choices is an LaTeXML::Core::Tokens.$keyword = $gullet->readKeyword(@keywords); Read and return whichever of @keywords (each a string) matches the input, or undef if none do. This is similar to readMatch, but case and catcodes are ignored. Also, leading spaces are skipped.$tokens = $gullet->readUntil(@delims); Read and return a (balanced) sequence of LaTeXML::Core::Tokens until matching one of the tokens in @delims. In a list context, it also returns which of the delimiters ended the sequence. ### High-level methods$tokens = $gullet->readArg; Read and return a TeX argument; the next Token or Tokens (if surrounded by braces).$tokens = $gullet->readOptional($default);

Read and return a LaTeX optional argument; returns $default if there is no ’[’, otherwise the contents of the [].$thing = $gullet->readValue($type);

Reads an argument of a given type: one of ’Number’, ’Dimension’, ’Glue’, ’MuGlue’ or ’any’.

$value =$gullet->readRegisterValue($type); Read a control sequence token (and possibly it’s arguments) that names a register, and return the value. Returns undef if the next token isn’t such a register.$number = $gullet->readNumber; Read a LaTeXML::Common::Number according to TeX’s rules of the various things that can be used as a numerical value.$dimension = $gullet->readDimension; Read a LaTeXML::Common::Dimension according to TeX’s rules of the various things that can be used as a dimension value.$mudimension = $gullet->readMuDimension; Read a LaTeXML::Core::MuDimension according to TeX’s rules of the various things that can be used as a mudimension value.$glue = $gullet->readGlue; Read a LaTeXML::Common::Glue according to TeX’s rules of the various things that can be used as a glue value.$muglue = \$gullet->readMuGlue;

Read a LaTeXML::Core::MuGlue according to TeX’s rules of the various things that can be used as a muglue value.