diff --git a/lama-spec.pdf b/lama-spec.pdf
index 9997b90fd..3ae1510aa 100644
Binary files a/lama-spec.pdf and b/lama-spec.pdf differ
diff --git a/spec/03.01.lexical_structure.tex b/spec/03.01.lexical_structure.tex
index 19d8276ce..e96298bcb 100644
--- a/spec/03.01.lexical_structure.tex
+++ b/spec/03.01.lexical_structure.tex
@@ -79,8 +79,8 @@ The following identifiers are reserved for keywords:
     after   array   at      before  boxed   case    do      elif    else
     esac    eta     false   fi      for     fun     if      import  infix
     infixl  infixr  lazy    length  local   od      of      public  repeat
-    return  sexp    skip    string  string  then    true    unboxed until
-    when    while
+    return  sexp    skip    string  string  syntax  then    true    unboxed
+    until   when    while
 \end{lstlisting}
 
 \subsection{Infix Operators}
diff --git a/spec/03.04.expressions.tex b/spec/03.04.expressions.tex
index 9d042d1c3..a89604d15 100644
--- a/spec/03.04.expressions.tex
+++ b/spec/03.04.expressions.tex
@@ -73,7 +73,7 @@ Multiple postfixes are allowed, for example
 The basic form of expression is \nonterm{primary}. The simplest form of primary is an identifier or constant. Keywords \lstinline|true| and \lstinline|false|
 designate integer constants 1 and 0 respectively, character constant is implicitly converted into its ASCII code.  String constants designate arrays
 of one-byte characters. Infix constants allow to reference a functional value associated with corresponding infix operator (however, a value associated with
-builtin assognment operator "\lstinline|:=|" can not be taken), and functional constant (\emph{lambda-expression})
+builtin assignment operator "\lstinline|:=|" can not be taken), and functional constant (\emph{lambda-expression})
 designates an anonymous functional value in the form of closure. 
 
 \begin{figure}[h]
diff --git a/spec/04.extensions.tex b/spec/04.extensions.tex
index 274497681..d87512282 100644
--- a/spec/04.extensions.tex
+++ b/spec/04.extensions.tex
@@ -131,3 +131,79 @@ is equivalent to
 
 where $x_i$~--- fresh variables, not free in $e$.
 
+\section{Syntax Definitions}
+
+Syntax definition extension represents an alternative simplified syntax for parsers written using standard unit \lstinline|Ostap| (see Section~\ref{sec:ostap}).
+The syntax for syntax definition expressions is shown on Fig.~\ref{syntax_expressions}.
+
+\begin{figure}[h]
+  \[
+    \begin{array}{rcll}
+      \defterm{syntaxExpression}  & : & \term{syntax}\s\term{(}\s\nonterm{syntaxSeq}\s(\s\term{$\mid$}\s\nonterm{syntaxSeq}\s)^*\s\term{)}&\\
+      \defterm{syntaxSeq}         & : & \nonterm{syntaxBinding}^+\s[\s\term{\{}\s\nonterm{expression}\s\term{\}}\s]&\\
+      \defterm{syntaxBinding}     & : & [\s\term{-}\s]\s[\s\nonterm{pattern}\s\term{=}\s]\s\s\nonterm{syntaxPostfix}&\\
+      \defterm{syntaxPostfix}     & : & \nonterm{syntaxPrimary}\s[\s\term{*}\s\alt\s\term{+}\s\alt\s\term{?}\s]&\\
+      \defterm{syntaxPrimary}     & : & \token{LIDENT}\s(\s\term{[}\s[\s\nonterm{expression}\s(\s\term{,}\s\nonterm{expression}\s)^*\s]\s\term{]}\s)^*&\alt\\
+                                  &   & \term{(}\s\nonterm{syntaxExpression}\s\term{)}&\alt\\
+                                  &   & \term{\$(}\s\nonterm{expression}\s\term{)}&
+    \end{array}
+  \]
+  \caption{Syntax definition expressions}
+  \label{syntax_expressions}
+\end{figure}
+
+Syntax expressions can be used wherever regular expressions are allowed. Each syntax expressions is expanded in a certain combination of \lstinline|Ostap| primitives.
+For example,
+
+\begin{lstlisting}
+    fun sum (str) {
+      parseString (
+        syntax (l=DECIMAL token["+"] r=DECIMAL eof {
+                  stringInt (l) + stringInt (r)
+               }),
+        str
+      )
+    }
+\end{lstlisting}
+
+defines a function which parses its arguments into an expression \lstinline|"l + r"|, where \lstinline|l| and \lstinline|r| are decimal literals, and evaluates its value.
+
+A syntax expression itself is a sequence of alternatives, and each alternative is a sequential composition (\nonterm{syntaxSeq}) of primitive parsers equipped with optional
+semantic action (a \emph{general} expression in curly brackets).
+
+A primitive parser is either an l-indentfier (possibly supplied with arguments), or a \emph{general} expression, surrounded by brackets \term{\$(}..\term{)},
+or a \emph{syntax} expression, surrounded by round brackets. Note, the arguments for primitive parsers in syntax expressions are surrounded by
+\term{[}..\term{]} unlike general expressions; thus
+
+\begin{lstlisting}
+   x ("a")
+\end{lstlisting}
+
+means a sequential composition of \lstinline|x| and "\lstinline|a|", not a combinator \lstinline|x| applied to "\lstinline|a|". 
+
+A primitive parser can be followed by one of postfix operators ("\term{*}", "\term{+}", or "\term{?}"), corresponding
+to "\lstinline|rep0|",  "\lstinline|rep|", or "\lstinline|opt|" combinators of \lstinline|Ostap| respectively, for example
+
+\begin{lstlisting}
+   token["a"]+
+   identifier? 
+\end{lstlisting}
+
+A value recognized by a primitive parser can be matched against a pattern, for example
+
+\begin{lstlisting}
+   value=(identifier | constant)
+   h:tl=item+
+\end{lstlisting}
+
+The bindings provided by pattern-matching can be used in semantic actions.
+
+Finally, if no semantic action is given, a sequential syntax expression returns a tuple of its components. However, if a parser
+in a sequential composition is preceded by "\term{-}" then its value is not included into the default result. Thus,
+
+\begin{lstlisting}
+   parse -eof
+\end{lstlisting}
+
+returns what "\lstinline|parse|" recognized; the input stream is parsed against "\lstinline|eof|", but the result of "\lstinline|eof|"
+is omitted.
diff --git a/spec/05.driver_options.tex b/spec/05.driver_options.tex
index 2da777e77..9a6c5f42e 100644
--- a/spec/05.driver_options.tex
+++ b/spec/05.driver_options.tex
@@ -1,7 +1,7 @@
 \chapter{Driver Options and Separate Compilation}
 \label{sec:driver}
 
-Driver is a command-line unitility "\texttt{lamac}" which controls the invocation of the compiler. The
+Driver is a command-line utility "\texttt{lamac}" which controls the invocation of the compiler. The
 general format of invocation is
 
 \begin{lstlisting}
diff --git a/spec/06.standard_library.tex b/spec/06.standard_library.tex
index eb0c12b1f..1661103f2 100644
--- a/spec/06.standard_library.tex
+++ b/spec/06.standard_library.tex
@@ -322,6 +322,7 @@ Return value represents parsing result as per "\lstinline|Ostap|".}
 \descr{\lstinline|fun getCol (m)|}{Gets a column number for the current position of matcher "\lstinline|m|".}
 
 \section{Unit \texttt{Ostap}}
+\label{sec:ostap}
 
 Unit "\lstinline|Ostap|" implements monadic parser combinators in continuation-passing style with memoization~\cite{MonPC,MemoParsing,Meerkat}.
 A parser is a function of the shape
@@ -349,6 +350,8 @@ The unit describes some primitive parsers and combinators which allow to constru
 
 \descr{\lstinline|fun empty (k)|}{A parser which recognizes empty string.}
 
+\descr{\lstinline|fun loc (k)|}{A parser which returns the current position (a pair "\lstinline|[line, col]|") in a stream.}
+
 \descr{\lstinline|fun alt (a, b)|}{A parser combinator which constructs a parser alternating between "\lstinline|a|" and "\lstinline|b|".}
 
 \descr{\lstinline|fun seq (a, b)|}{A parser combinator which construct a sequential composition of "\lstinline|a|" and "\lstinline|b|". While
@@ -393,11 +396,11 @@ parser which behaves exactly as "\lstinline|a|", but additionally applies "\lsti
 
 \begin{lrbox}{\exprbox}
 \begin{lstlisting}
-    {[Left, {[token ("+"), fun (l, r) {Add (l, r)}],
-             [token ("-"), fun (l, r) {Sub (l, r)}]
+    {[Left, {[token ("+"), fun (l, op, r) {Add (l, r)}],
+             [token ("-"), fun (l, op, r) {Sub (l, r)}]
             }],
-     [Left, {[token ("*"), fun (l, r) {Mul (l, r)}],
-             [token ("/"), fun (l, r) {Div (l, r)}]
+     [Left, {[token ("*"), fun (l, op, r) {Mul (l, r)}],
+             [token ("/"), fun (l, op, r) {Div (l, r)}]
             }]}
 \end{lstlisting}
 \end{lrbox}
@@ -405,12 +408,14 @@ parser which behaves exactly as "\lstinline|a|", but additionally applies "\lsti
 \descr{\lstinline|fun expr (ops, opnd)|}{A super-combinator to generate infix expression parsers. The argument "\lstinline|opnd|" parses primary operand, "\lstinline|ops|" is
   a list of infix operator descriptors. Each element of the list describes one \emph{precedence level} with precedence increasing from head to tail. A descriptor on
   each level is a pair, where the first element describes the associativity at the given level ("\lstinline|Left|", "\lstinline|Right|" or "\lstinline|None|") and
-  the second element is a list of pairs~--- a parser for an infix operator and the semantics action (a two-argument function). For example,
+  the second element is a list of pairs~--- a parser for an infix operator and the semantics action (a three-argument function accepting the left parser operand, that that
+  infix operator parser returns, and the right operand). For example,
 
   \usebox\exprbox
 
   specifies two levels of precedence, both left-associative, with infix operators "\lstinline|+|" and "\lstinline|-|" at the first level and
-  "\lstinline|*|" and "\lstinline|/|" at the second. The semantics for these operators constructs abstract sytax trees.
+  "\lstinline|*|" and "\lstinline|/|" at the second. The semantics for these operators constructs abstract syntax trees (in this particular example the
+  second argument of semantics functions is unused).
 }
 
 \section{Unit \texttt{Ref}}