Let-expr to the spec

spec/03.04.expressions.tex

@@ -141,7 +141,33 @@ There are three forms of expressions to specify composite values: arrays, lists
 
 \subsection{Let Expressions}
 
-TODO
+\begin{figure}[h]
+  \[
+  \begin{array}{rcll}
+    \defterm{letExpression} & : & \term{let}\s\nonterm{pattern}\s\term{=}\s\nonterm{expression}\s\term{in}\s\nonterm{expression}
+  \end{array}
+  \]
+  \caption{Let-expression syntax}
+  \label{let_expression}
+\end{figure}
+
+Let expression is a derived syntactic form for a one-branch case-expression. An expression
+
+\begin{lstlisting}
+   let p = e in b
+\end{lstlisting}
+
+is equivalent to
+
+\begin{lstlisting}
+   case e of
+     p -> b
+   esac
+\end{lstlisting}
+
+As let expression lacks an explicit ending specifier its scope extends to the right while possible; multiple let expressions on
+the same nesting level associate to the right.
+
 
 \FloatBarrier
 

spec/08.standard_library.tex

@@ -95,8 +95,8 @@ is automatically created and closed within the call.}
 \descr{\lstinline|fun fprintf (file, fmt, ...)|}{Same as "\lstinline|printf|", but outputs to a given file. The file argument should be that acquired
   by \lstinline|fopen| function.}
 
-\descr{\lstinline|fun regexp (str)|}{Compiles a string representation of a regular expression (as per POSIX-Extended Regular Expressions syntax) into
+\descr{\lstinline|fun regexp (string)|}{Compiles a string representation of a regular expression (as per POSIX-Extended Regular Expressions syntax) into
-  an internal representation. The return value is a external pointer to the internal representation.}
+  an internal representation. The return value is an external pointer to the internal representation.}
 
 \descr{\lstinline|fun regexpMatch (pattern, subj, pos)|}{Matches a string "\lstinline{subj}", starting from the position "\lstinline|pos|",
   against a pattern "\lstinline{pattern}". The pattern is an external pointer to a compiled representation, returned by the