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Dmitry Boulytchev
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110
doc/spec/03.01.lexical_structure.tex
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110
doc/spec/03.01.lexical_structure.tex
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\section{Lexical Structure}
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The character set for the language is \textsc{ASCII}, case-sensitive. In the following lexical description we will use
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the GNU Regexp syntax~\cite{GNULib} in lexical definitions.
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\subsection{Whitespaces and Comments}
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Whitespaces and comments are \textsc{ASCII} sequences which serve as delimiters for other tokens but otherwise are
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ignored.
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The following characters are treated as whitespaces:
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\begin{itemize}
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\item blank character "\texttt{ }";
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\item newline character "\texttt{\textbackslash n}";
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\item tabulation character "\texttt{\textbackslash t}".
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\end{itemize}
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Additionally, two kinds of comments are recognized:
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\begin{itemize}
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\item end-of-line comment "\texttt{--}" escapes the rest of the line, including itself;
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\item block comment "\texttt{(*} ... \texttt{*)}" escapes all the text between
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"\texttt{(*}" and "\texttt{*)}".
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\end{itemize}
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There is a number of specific cases which have to be considered explicitly.
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First, block comments can be properly nested. Then, the occurencies of comment symbols inside string literals (see below) do not
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considered as comments.
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End-of-line comment encountered \emph{outside} of a block comment escapes block comment symbols:
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\begin{lstlisting}
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-- the following symbols are not considered as a block comment: (*
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-- same here: *)
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\end{lstlisting}
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Similarly, an end-of-line comment encountered inside a block comment is escaped:
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\begin{lstlisting}
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(* Block comment starts here ...
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-- and ends here: *)
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\end{lstlisting}
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\subsection{Identifiers and Constants}
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The language distinguishes identifiers, signed decimal literals, string and character literals (see Fig.~\ref{idents_and_consts}). There are
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two kinds of identifiers: those beginning with uppercase characters (\token{UIDENT}) and lowercase characters (\token{LIDENT}).
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String literals cannot span multiple lines; a blockquote character (") inside a string literal has to be doubled to prevent from
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being considered as this literal's delimiter.
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Character literals as a rule are comprised of a single \textsc{ASCII} character; if this character is a quote (') it has to be doubled. Additionally
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two-character abbreviations "\textbackslash t" and "\textbackslash n" are recognized and converted into a single-character representation.
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\begin{figure}[t]
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\[
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\begin{array}{rcl}
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\token{UIDENT} & = &\mbox{\texttt{[A-Z][a-zA-Z\_0-9]*}}\\
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\token{LIDENT} & = &\mbox{\texttt{[a-z][a-zA-Z\_0-9]*}}\\
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\token{DECIMAL}& = &\mbox{\texttt{-?[0-9]+}}\\
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\token{STRING} & = &\mbox{\texttt{"([\^{}\textbackslash"]|"")*"}}\\
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\token{CHAR} & = &\mbox{\texttt{'([\^{}']|''|\textbackslash n|\textbackslash t)'}}
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\end{array}
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\]
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\caption{Identifiers and constants}
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\label{idents_and_consts}
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\end{figure}
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\subsection{Keywords}
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The following identifiers are reserved for keywords:
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\begin{lstlisting}
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after array at before boxed case do elif else
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esac false fi for fun if import infix infixl
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infixr length local od of public repeat return sexp
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skip string string then true unboxed until when while
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\end{lstlisting}
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\subsection{Infix Operators}
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Infix operators defined as follows:
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\[
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\token{INFIX}=\mbox{\texttt{[+*/\%\$\#@!|\&\^{}~?<>:=\textbackslash-]+}}
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\]
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There is a predefined set of built-in infix operators (see~\ref{binary_expressions}); additionally
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an end-used can define custom infix operators (see~\ref{custom_infix}). Note, sometimes
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additional whitespaces are required to disambiguate infix operator applications. For example, if a
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custom infix operator "\lstinline|+-|" is defined, then the expression "\lstinline|a +- b|" can no longer be
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considered as "\lstinline|a +(-b)|". Note also that a custom operator "\lstinline|--|" can not be
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defined due to lexical conventions.
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\subsection{Delimiters}
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The following symbols are treated as delimiters:
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\begin{lstlisting}
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. , ( ) { }
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; # ->
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\end{lstlisting}
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Despite custom infix operators can coincide with delimiters "\lstinline|#|" and "\lstinline|->|" they can
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never clash as both these delimiters can not be encountered in expressions.
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21
doc/spec/03.02.compilation_units.tex
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21
doc/spec/03.02.compilation_units.tex
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\begin{figure}[t]
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\[
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\begin{array}{rcl}
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\defterm{compilationUnit} & : & \nonterm{import}^\star\s\nonterm{scopeExpression}\\
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\defterm{import} & : & \term{import}\s\token{UIDENT}\s\term{;}
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\end{array}
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\]
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\caption{Compilation unit concrete syntax}
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\label{compilation_unit}
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\end{figure}
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\section{Compilation Units}
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Compilation unit is a minimal structure recognized by a parser. An application can contain multiple units, compiled separatedly.
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In order to use other units they have to be imported. In particular, the standard library is comprized of a number of precompiled units,
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which can be imported by an end-user application.
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The concrete syntax for compilation unit is show on Fig.~\ref{compilation_unit}. Besides optional imports a unit must contain
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a \nonterm{scopeExpression}, which may contain some definitions and computations. Note, a unit can not be empty. The computations described in
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a unit are performed at unit initialization time (see~\ref{separate_compilation}).
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105
doc/spec/03.03.scope_expressions.tex
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105
doc/spec/03.03.scope_expressions.tex
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\begin{figure}[t]
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\[
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\begin{array}{rcl}
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\defterm{scopeExpression} & : & \nonterm{definition}^\star\s\nonterm{expression}\\
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\defterm{definition} & : & \nonterm{variableDefinition}\alt\nonterm{functionDefinition}\alt\nonterm{infixDefinition}\\
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\defterm{variableDefinition} & : & (\s\term{local}\alt\term{public}\s)\s\nonterm{variableDefinitionSequence}\s\term{;}\\
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\defterm{variableDefinitionSequence} & : & \nonterm{variableDefinitionSequenceItem}\s(\s\term{,}\s\nonterm{variableDefinitionSequenceItem}\s)^\star\\
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\defterm{variableDefinitionSequenceItem} & : & \token{LIDENT}\s[\s\term{=}\s\nonterm{basicExpression}\s]\\
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\defterm{functionDefinition} & : & [\s\term{public}\s]\s\term{fun}\s\token{LIDENT}\s\term{(}\s\nonterm{functionArguments}\s\term{)}\s\nonterm{functionBody}\\
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\defterm{functionArguments} & : & [\s\token{LIDENT}\s(\s\term{,}\s\token{LIDENT}\s)^\star\s]\\
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\defterm{functionBody} & : & \term{\{}\s\nonterm{scopeExpression}\s\term{\}}
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\end{array}
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\]
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\caption{Scope expression concrete syntax}
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\label{scope_expression}
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\end{figure}
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\section{Scope Expressions}
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Scope expressions provide a mean to put expressions is a scoped context. The definitions in scoped expressions comprise of function definitions and
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variable definitions (see Fig.~\ref{scope_expression}). For example:
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\begin{lstlisting}
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local x, y, z; -- variable definitions
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fun id (x) {x} -- function definition
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\end{lstlisting}
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As scope expressions are expressions, they can be nested:
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\begin{lstlisting}
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local x;
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{ -- nested scope begins here
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local y;
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skip
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} -- nested scope ends here
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\end{lstlisting}
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The definitions on the top-level of compilation unit can be tagged as ``\lstinline|public|'', in which case they are exported and become visible by
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other units which import the given one. Nested scopes can not contain public definitions.
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The nesting relation has the shape of a tree, and in a concrete node of the tree all definitions in all enclosing scopes are visible:
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\begin{lstlisting}
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local x;
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{local y;
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{local z;
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skip -- x, y, and z are visible here
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};
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{local t;
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skip -- x, y, and t are visible here
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};
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skip -- x and y are visible here
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};
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skip -- only x is visible here
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\end{lstlisting}
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Multiple definitions of the same name in the same scope are prohibited:
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\begin{lstlisting}
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local x;
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fun x () {0} -- error
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\end{lstlisting}
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However, a definition is a nested scope can override a definition in an enclosing one:
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\begin{lstlisting}
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local x;
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{
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fun x () {0} -- ok
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skip -- here x is associated with the function
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};
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skip -- here x is asociated with the variable
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\end{lstlisting}
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A function can freely use all visible definitions; in particular, functions defined in the
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same scope can be mutually recursive:
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\begin{lstlisting}
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local x;
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fun f () {0}
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{
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fun g () {f () + h () + y} -- ok
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fun h () {g () + x} -- ok
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local y;
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skip
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};
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skip
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\end{lstlisting}
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A variable, defined in a scope, can be attributed with an expression, calcualting its initial value.
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These expressions, however, are evaluated in the order of variable declaration. Thus, while
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technically it is possible to have forward references in the initialization expression, their
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behaviour is undefined. For example:
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\begin{lstlisting}
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local x = y + 2; -- undefined, as y is not yet initialized at this point
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local y = x + 2;
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skip
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\end{lstlisting}
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45
doc/spec/03.04.expressions.tex
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45
doc/spec/03.04.expressions.tex
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@ -0,0 +1,45 @@
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\begin{figure}[t]
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\[
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\begin{array}{rcll}
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\defterm{expression} & : & \nonterm{basicExpression}\s(\s\term{;}\s\nonterm{expression}\s)&\\
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\defterm{basicExpression} & : & \nonterm{binaryExpression}&\\
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\defterm{binaryExpression} & : & \nonterm{binaryOperand}\s\token{INFIX}\s\nonterm{binaryOperand}&\alt\\
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& & \nonterm{binaryOperand}&\\
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\defterm{binaryOperand} & : & \nonterm{binaryExpression}&\alt\\
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& & [\s\term{-}\s]\s\nonterm{postfixExpression}&\\
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\defterm{postfixExpression} & : & \nonterm{primary}&\alt\\
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& & \nonterm{postfixExpression}\s\term{(}\s[\s\nonterm{expression}\s(\s\term{,}\s\nonterm{expression}\s)^\star\s]\s\term{)}&\alt\\
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& & \nonterm{postfixExpression}\s\term{[}\s\nonterm{expression}\s\term{]}&\alt\\
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& & \nonterm{postfixExpression}\s\term{.}\s\term{length}&\alt\\
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& & \nonterm{postfixExpression}\s\term{.}\s\term{string}&\\
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\defterm{primary} & : & \token{DECIMAL}&\alt\\
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& & \token{STRING}&\alt\\
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& & \token{CHAR}&\alt\\
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& & \token{LIDENT}&\alt\\
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& & \term{true}&\alt\\
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& & \term{false}&\alt\\
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& & \term{infix}\s\token{INFIX}&\alt\\
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& & \term{skip}&\alt\\
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& & \term{return}\s[\s\nonterm{basicExpression}\s]&\alt\\
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& & \term{fun}\s\term{(}\s\nonterm{functionArguments}\s\term{)}\s\nonterm{functionBody}&\alt\\
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& & \term{\{}\s\nonterm{scopeExpression}\s\term{\}}&\alt\\
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& & \nonterm{listExpression}&\alt\\
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& & \nonterm{arrayExpression}&\alt\\
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& & \nonterm{S-expression}&\alt\\
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& & \nonterm{ifExpression}&\alt\\
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& & \nonterm{whileExpression}&\alt\\
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& & \nonterm{repeatExpression}&\alt\\
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& & \nonterm{forExpression}&\alt\\
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& & \nonterm{caseExpression}&\alt\\
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& & \term{(}\s\nonterm{expression}\s\term{)}&
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\end{array}
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\]
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\caption{Expression concrete syntax}
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\label{expressions}
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\end{figure}
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\section{Expressions}
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\label{sec:expressions}
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Expressions
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@ -1,71 +1,26 @@
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\chapter{Concrete Syntax}
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\begin{figure}[t]
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\[
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\begin{array}{rcl}
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\defterm{compilationUnit} & : & \nonterm{import}^\star\s\nonterm{scopeExpression}\\
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\defterm{import} & : & \term{import}\s\token{UIDENT}\s\term{;}
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\end{array}
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\]
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\caption{Compilation unit concrete syntax}
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\end{figure}
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In this chapter we describe the concrete syntax of the language as it is recognized by the parser. In the
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syntactic description we will use extended Backus-Naur form with the following conventions:
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\begin{figure}[t]
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\[
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\begin{array}{rcll}
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\defterm{expression} & : & \nonterm{basicExpression}\s(\s\term{;}\s\nonterm{expression}\s)&\\
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\defterm{basicExpression} & : & \nonterm{binaryExpression}&\\
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\defterm{binaryExpression} & : & \nonterm{binaryOperand}\s\token{INFIX}\s\nonterm{binaryOperand}&\alt\\
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& & \nonterm{binaryOperand}&\\
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\defterm{binaryOperand} & : & \nonterm{binaryExpression}&\alt\\
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& & [\s\term{-}\s]\s\nonterm{postfixExpression}&\\
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\defterm{postfixExpression} & : & \nonterm{primary}&\alt\\
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& & \nonterm{postfixExpression}\s\term{(}\s[\s\nonterm{expression}\s(\s\term{,}\s\nonterm{expression}\s)^\star\s]\s\term{)}&\alt\\
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& & \nonterm{postfixExpression}\s\term{[}\s\nonterm{expression}\s\term{]}&\alt\\
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& & \nonterm{postfixExpression}\s\term{.}\s\term{length}&\alt\\
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& & \nonterm{postfixExpression}\s\term{.}\s\term{string}&\\
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\begin{itemize}
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\item nonterminals are presented in \nonterm{italics};
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\item concrete terminals are \term{grayed out};
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\item classes of terminals are \token{CAPITALIZED};
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\item a postfix ``$^\star$'' designates zero-or-more repetitions;
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\item square brackets ``$[\dots]$'' designate zero-or-one repetition;
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\item round brackets ``$(\dots)$'' are used for grouping;
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\item alteration is denoted by ``$\alt$'', sequencing by juxaposition;
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\item a colon ``$:$'' separates a nonterminal being defined from its definition.
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\end{itemize}
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\defterm{primary} & : & \token{DECIMAL}&\alt\\
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& & \token{STRING}&\alt\\
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& & \token{CHAR}&\alt\\
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& & \token{LIDENT}&\alt\\
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& & \term{true}&\alt\\
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& & \term{false}&\alt\\
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& & \term{infix}\s\token{INFIX}&\alt\\
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& & \term{skip}&\alt\\
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& & \term{fun}\s\term{(}\s\nonterm{functionArguments}\s\term{)}\s\nonterm{functionBody}&\alt\\
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& & \term{\{}\s\nonterm{scopeExpression}\s\term{\}}&\alt\\
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& & \nonterm{listExpression}&\alt\\
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& & \nonterm{arrayExpression}&\alt\\
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& & \nonterm{S-expression}&\alt\\
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& & \nonterm{ifExpression}&\alt\\
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& & \nonterm{whileExpression}&\alt\\
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& & \nonterm{repeatExpression}&\alt\\
|
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& & \nonterm{forExpression}&\alt\\
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& & \nonterm{caseExpression}&\alt\\
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& & \term{(}\s\nonterm{expression}\s\term{)}&
|
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\end{array}
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\]
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\caption{Expression concrete syntax}
|
||||
\end{figure}
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||||
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||||
|
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\begin{figure}[t]
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\[
|
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\begin{array}{rcl}
|
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\defterm{scopeExpression} & : & \nonterm{definition}^\star\s\nonterm{expression}\\
|
||||
\defterm{definition} & : & \nonterm{variableDefinition}\alt\nonterm{functionDefinition}\alt\nonterm{infixDefinition}\\
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\defterm{variableDefinition} & : & (\s\term{local}\alt\term{public}\s)\s\nonterm{variableDefinitionSequence}\s\term{;}\\
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\defterm{variableDefinitionSequence} & : & \nonterm{variableDefinitionSequenceItem}\s(\s\term{,}\s\nonterm{variableDefinitionSequenceItem}\s)^\star\\
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\defterm{variableDefinitionSequenceItem} & : & \token{LIDENT}\s[\s\term{=}\s\nonterm{basicExpression}\s]\\
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\defterm{functionDefinition} & : & [\s\term{public}\s]\s\term{fun}\s\token{LIDENT}\s\term{(}\s\nonterm{functionArguments}\s\term{)}\s\nonterm{functionBody}\\
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\defterm{functionArguments} & : & [\s\token{LIDENT}\s(\s\term{,}\s\token{LIDENT}\s)^\star\s]\\
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\defterm{functionBody} & : & \term{\{}\s\nonterm{scopeExpression}\s\term{\}}
|
||||
\end{array}
|
||||
\]
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\caption{Scope expression concrete syntax}
|
||||
\end{figure}
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In the description below we will take an in-line code samples in blockquotes "..." which are not considered as a
|
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part of concrete syntax.
|
||||
|
||||
\input{03.01.lexical_structure}
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||||
\input{03.02.compilation_units}
|
||||
\input{03.03.scope_expressions}
|
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\input{03.04.expressions}
|
||||
|
||||
\begin{figure}[t]
|
||||
\[
|
||||
|
|
|
|||
6
doc/spec/spec.bib
Normal file
6
doc/spec/spec.bib
Normal file
|
|
@ -0,0 +1,6 @@
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@manual{GNULib,
|
||||
title = "{The GNU Portability Library}",
|
||||
organization = "{Free Software Foundation}",
|
||||
bibdate = "February 24, 2019",
|
||||
bibsource = "https://www.gnu.org/software/gnulib/manual"
|
||||
}
|
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|
|
@ -86,30 +86,32 @@
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|||
\newcommand{\alt}{\s\mid\s}
|
||||
\newcommand{\s}{\:\:}
|
||||
|
||||
\lstdefinelanguage{lama}{
|
||||
keywords={fun, case, esac, do, od, if, then, else, elif, fi, skip, repeat, until, for, local},
|
||||
\lstdefinelanguage{alm}{
|
||||
keywords={skip,if,then,else,elif,fi,while,do,od,repeat,until,for,fun,local,public,return,import,length,
|
||||
string,case,of,esac,when,boxed,unboxed,string,sexp,array,infix,infixl,infixr,at,before,after,true,false},
|
||||
sensitive=true,
|
||||
%basicstyle=\small,
|
||||
commentstyle=\scriptsize\rmfamily,
|
||||
basicstyle=\small,
|
||||
%commentstyle=\scriptsize\rmfamily,
|
||||
keywordstyle=\ttfamily\bfseries,
|
||||
identifierstyle=\ttfamily,
|
||||
basewidth={0.5em,0.5em},
|
||||
columns=fixed,
|
||||
fontadjust=true,
|
||||
literate={->}{{$\to$}}3,
|
||||
morecomment=[s]{(*}{*)}
|
||||
morecomment=[s][\ttfamily]{(*}{*)},
|
||||
morecomment=[l][\ttfamily]{--}
|
||||
}
|
||||
|
||||
\lstset{
|
||||
mathescape=true,
|
||||
%basicstyle=\small,
|
||||
basicstyle=\small,
|
||||
identifierstyle=\ttfamily,
|
||||
keywordstyle=\bfseries,
|
||||
commentstyle=\scriptsize\rmfamily,
|
||||
basewidth={0.5em,0.5em},
|
||||
fontadjust=true,
|
||||
escapechar=!,
|
||||
language=lama
|
||||
language=alm
|
||||
}
|
||||
|
||||
\sloppy
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue