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1.1       root        1: \chapter{Standard bindings}
                      2: ML provides the record type constructor 
                      3: $ \verb"{" {\bf lab}_1 \verb":" {\bf ty}_1 , \underline{\ \ \ }
                      4:  , {\bf lab}_n \verb":" {\bf ty}_n \verb"}"$ for any set 
                      5: $\{ {\bf lab}_i \} $ of labels and corresponding set 
                      6: $\{ {\bf ty}_i \} $ of types.  The language also provides the infixed
                      7: function-type constructor \verb"->".  Otherwise, type constructors
                      8: are postfixed.  The following are standard:
                      9: 
                     10: \begin{description}
                     11: \item[Type {\em constants} (nullary constructors):]  unit, bool, exn, int,
                     12: real, string, instream, outstream
                     13: \item[Unary type constructors:]  list, ref
                     14: \end{description}
                     15: 
                     16: The constructors unit, bool, and list are fully defined by the
                     17: following assumed declaration
                     18: \begin{verbatim}
                     19: infixr 5 ::
                     20: type unit = {}
                     21: datatype    bool = true | false
                     22: datatype  'a list = nil |  :: of {1 : 'a, 2 : 'a list}
                     23: \end{verbatim}
                     24: 
                     25: The word ``unit'' is chosen since the type contains just one value
                     26: ``\verb"{}"'', the empty record.  This is why it is preferred to the
                     27: word ``void'' of Algol-68.
                     28: 
                     29: The type constants \verb"int", \verb"real", and \verb"string"
                     30: are equipped with special
                     31: constants as described in section 2.3.  The type constructor
                     32: \verb"ref" is for constructing reference types; see
                     33: Chapter~\ref{reference}.
                     34: The type constant \verb"exn" is the type of all exceptions, and
                     35: is a datatype containing an unbounded number of constructors
                     36: generated by \verb"exception" bindings (see Chapter~\ref{exception}).
                     37: 
                     38: 
                     39: 
                     40: The initial top-level environment is comprised of a set of standard
                     41: bindings.  The initial environment is much more extensive than the
                     42: environment described in {\it The Definition of Standard ML}, and
                     43: is almost a proper superset.  The differences are:
                     44: 
                     45: \begin{itemize}
                     46: \item All values, types, datatypes, etc. are grouped into structures;
                     47: these structures are opened in the initial environment so that the
                     48: names can be used without a structure-name qualification.
                     49: 
                     50: \item There are many additional initial bindings, described in 
                     51: Appendix~\ref{library}.
                     52: 
                     53: \item The functions \verb"input" and \verb"output" are curried in Standard
                     54: ML of New Jersey, e.g. \verb"input: instream->int->string" instead of
                     55: \verb"input: instream*int->string".
                     56: 
                     57: \item The integer functions \verb"+", \verb"-", \verb"div", \verb"mod", 
                     58: \verb"*", \verb"~", \verb"abs" all raise \verb"Overflow" if the result is out-of-range,
                     59: rather than \verb"Sum", \verb"Diff", \verb"Div", \verb"Mod", \verb"Prod",
                     60: \verb"Neg", \verb"Abs", respectively.
                     61: 
                     62: \item The integer \verb"div" function rounds toward zero, and \verb"x mod y"
                     63: is defined as \verb"x-y*(x div y)".
                     64: 
                     65: \end{itemize}
                     66: 
                     67: Standard ML of New Jersey is distributed with a structure \verb"Standard"
                     68: that may be loaded into the initial environment to simulate
                     69: environment described in the {\it Definition}.

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