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\chapter{Syntax of the pretty-printing language}
\newcommand\object[1]{\item[\small\tt #1\hfill]}
\section{Lexical objects}
\begin{list}{}
{\setlength{\leftmargin}{10em}
\setlength{\labelwidth}{10em}
\addtolength{\labelwidth}{-\labelsep}}
\object{<number>}
A sequence of one or more decimal digits.
\object{<identifier>}
A letter followed by zero or more occurrences of a letter or a digit or an
underscore followed by a letter or a digit.
\object{<string>}
Any sequence of characters not containing line-feed, form-feed or
carriage-return, enclosed within single quotation-marks, for example
{\small\verb|'2fg F%01'|}. Two consequtive single quotes are interpreted as one
single quote which appears in the string, e.g.~{\small\verb%'a''b'%} is
interpreted as the string {\small\verb%a'b%}.
\object{<terminal>}
As for {\small\verb%<string>%} but with double quotation-marks rather than
single quotation-marks.
\object{<comment>}
Any sequence of characters enclosed within percent signs ({\small\verb|%|}).
{\small\verb|%%|} within the character sequence is interpreted as
{\small\verb|%|}. Comments are ignored.
\object{<id\_quote>}
Any sequence of characters not containing line-feed, form-feed or
carriage-return, enclosed within sharp signs ({\small\verb%#%}).
{\small\verb%##%} within the character sequence is interpreted as
{\small\verb%#%}. The text within the sharp signs is made into an identifier.
This allows non-alphanumeric characters and keywords to be used as identifiers.
\object{<ML\_function>}
Any sequence of characters enclosed within braces. Line-feed, form-feed
and carriage-return may appear. {\small\verb%{{%} is interpreted as
{\small\verb%{%}. {\small\verb%}}%} is interpreted as {\small\verb%}%}.
{\small\verb%{%} causes an error.
\object{<special>}
A special symbol. The special symbols are:
\begin{small}\begin{verbatim}
+ - * ** *** , ; : :: = := -> ..
( ) **[ [ ] < > << >> |
\end{verbatim}\end{small}
\object{<keyword>}
A keyword. The keywords are:
\begin{small}\begin{verbatim}
prettyprinter rules declarations
abbreviations with end where
if then else h v hv hov
\end{verbatim}\end{small}
\end{list}
In the grammar that follows, special symbols and keywords appear in
double quotation-marks.
\section{The grammar}
\begin{small}\begin{verbatim}
<integer> ::= <number> | "-" <number>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<name_metavar> ::= "***" | "***" <identifier>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<child_metavar> ::= "*" | "*" <identifier>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<children_metavar> ::= "**" | "**" <identifier>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<metavar_list> ::= <name_metavar>
| <child_metavar>
| <children_metavar>
| <name_metavar> ";" <metavar_list>
| <child_metavar> ";" <metavar_list>
| <children_metavar> ";" <metavar_list>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<min> ::= <number>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<max> ::= <number>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<loop_range> ::= <min> ".."
| ".." <max>
| <min> ".." <max>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<loop_link> ::= "<" ">"
| "<" <metavar_list> ">"
| "<" <loop_range> ">"
| "<" <loop_range> ":" <metavar_list> ">"
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<label> ::= "|" <child_metavar> "|"
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<node_name> ::= <identifier> | <name_metavar>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<child> ::= <children_metavar>
| <pattern_tree>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<child_list> ::= <child>
| <child> "," <child_list>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<pattern_tree> ::= <node_name> "(" ")"
| <node_name> "(" <child_list> ")"
| <child_metavar>
| <label> <pattern_tree>
| <loop_link>
| <loop_link> <pattern_tree>
| <loop>
| <loop> <pattern_tree>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<loop> ::= "[" <pattern_tree> "]"
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<test> ::= <ML_function> | <identifier>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<pattern> ::= <string> "::" <pattern_tree>
| <string> "::" <pattern_tree> "where" <test>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<transformation> ::= <ML_function> | <identifier>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<p_special> ::= <name_metavar> "=" <transformation>
| <child_metavar> "=" <transformation>
| <children_metavar> "=" <transformation>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<p_special_list> ::= <p_special>
| <p_special> ";" <p_special_list>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<int_expression> ::= <integer> | <ML_function> | <identifier>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<assignment> ::= <identifier> ":=" <int_expression>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<assignments> ::= <assignment>
| <assignment> ";" <assignments>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<fun_subcall> ::= <name_metavar>
| <child_metavar>
| <children_metavar>
| <transformation> "(" <name_metavar> ")"
| <transformation> "(" <child_metavar> ")"
| <transformation> "(" <children_metavar> ")"
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<context_subcall> ::= <fun_subcall>
| <string> "::" <fun_subcall>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<leaf_or_subcall> ::= <context_subcall>
| <context_subcall>
"with" <assignments> "end" "with"
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<indent> ::= <integer> | "+" <integer>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<h_params> ::= <number>
<v_params> ::= <indent> "," <number>
<hv_params> ::= <number> "," <indent> "," <number>
<hov_params> ::= <number> "," <indent> "," <number>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<h_box> ::= "h" <h_params>
<v_box> ::= "v" <v_params>
<hv_box> ::= "hv" <hv_params>
<hov_box> ::= "hov" <hov_params>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<object> ::= <terminal>
| <leaf_or_subcall>
| <format>
| <expand>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<h_object> ::= <object> | "<" <h_params> ">" <object>
<v_object> ::= <object> | "<" <v_params> ">" <object>
<hv_object> ::= <object> | "<" <hv_params> ">" <object>
<hov_object> ::= <object> | "<" <hov_params> ">" <object>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<h_object_list> ::= <h_object> | <h_object> <h_object_list>
<v_object_list> ::= <v_object> | <v_object> <v_object_list>
<hv_object_list> ::= <hv_object> | <hv_object> <hv_object_list>
<hov_object_list> ::= <hov_object> | <hov_object> <hov_object_list>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<box_spec> ::= "<" <h_box> ">" <h_object_list>
| "<" <v_box> ">" <v_object_list>
| "<" <hv_box> ">" <hv_object_list>
| "<" <hov_box> ">" <hov_object_list>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<expand> ::= "**[" <box_spec> "]"
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<format> ::= "[" "]"
| "[" <box_spec> "]"
| "if" <test> "then" <format> "else" <format>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<rule> ::= <pattern> "->" <format>
| <pattern> "->"
"<<" <p_special_list> ">>" <format>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<rule_list> ::= <rule> ";" | <rule> ";" <rule_list>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<rules> ::= "rules" <rule_list> "end" "rules"
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<binding> ::= <identifier> "=" <ML_function>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<binding_list> ::= <binding> ";"
| <binding> ";" <binding_list>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<declarations> ::= "declarations" <binding_list>
"end" "declarations"
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<abbreviations> ::= "abbreviations" <binding_list>
"end" "abbreviations"
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<body> ::= <rules>
| <declarations> <rules>
| <abbreviations> <rules>
| <declarations> <abbreviations> <rules>
\end{verbatim}\end{small}
\begin{small}\begin{verbatim}
<pp> ::= "prettyprinter" <identifier> "="
<body>
"end" "prettyprinter"
\end{verbatim}\end{small}
|
