the
language

^________ Overview ^{____________________________________________________}

Alice ML is based on the Standard ML programming language (SML), as defined in

• Robin Milner, Mads Tofte, Robert Harper, Dave MacQueen:
  The Definition of Standard ML (Revised)
  The MIT Press
  ISBN 0-262-63181-4

However, Alice ML features a number of extensions relative to SML (including most current proposals for Successor ML).

• Futures:
  • concurrency
  • lazy evaluation
  • promises
• Extended type language:
  • structural datatypes
  • extensible types
  • type wildcards
• Higher-order modules:
  • local modules
  • generalised open declarations
  • higher-order functors
  • signature members and abstract signatures
  • lazy evaluation
  • fixity specifications
  • syntax enhancements
• Packages:
  • first-class modules
  • dynamic typing
• Pickling:
  • persistent values
  • persistent modules
• Components:
  • separate compilation
  • lazy linking
  • first-class components
  • sandboxing
• Distributed programming:
  • tickets
  • proxies
• Constraint programming
  • finite domain constraints
  • finite set contraints
  • first-class computation spaces
• Syntactic sugar:
  • line comments
  • extended syntax for numeric literals
  • vector expressions and patterns
  • sugar for records
  • extended pattern language
  • generalized recursive definitions
  • Optional bars and semicolons
  • conditional with optional else branch
  • finalization
  • source position
  • assertions
  • statements

You should also be aware of some

• incompatibilities with SML,
• limitations of the current implementation.

^________ Syntax summary ^{______________________________________________}

Line comments

• The comment marker (*) introduces a line comment.

Literals

• Numeric literals may contain underscores to group digits.
• The prefixes 0b and 0wb introduce binary literals.

Reserved words

Alice ML defines some additional identifiers as reserved words:

	any assert assertd comp constructor exttype
	fct finally from import non lazy
	pack spawn unpack withfun withval _file_ _line_

The following grammar collects all other syntactic extensions of Alice ML relative to Standard ML. Derived forms are marked (*).

Long identifiers

Expressions

¹) The syntax of import items in a first-class component is restricted to the syntactic subclass of the corresponding descriptions, as used in signatures.

Patterns

Types

Declarations

extbind ::= tyvarseq tycon extensible datatype

econbind ::= <op> vid <of ty> : tyvarseq longtycon <and econbind> new constructor

<op> vid = <op> longvid <and econbind> synonym

strbind ::= ...

_ <: sigexp> = strexp <and strbind> anonymous structure (*)

funbind ::= <lazy | spawn> strid strpat₁ ... strpat_n < : | :> sigexp> = strexp <and funbind> functor binding (n≥1) (*) ²

¹) The extended phrase class dec contains all of Standard ML's dec, strdec and topdec.

²) See the module syntax summary for a more precise grammar of functor bindings.

Structures

strexp ::= ...

( strexp ) parentheses

( dec ) structure (*)

strexp strexp functor application ¹

fct strpat => strexp functor

unpack infexp : sigexp unpacking

lazy strexp laziness

spawn strexp concurrency

strpat ::= strid : sigexp parameter

_ : sigexp anonymous parameter (*)

( strid : sigexp ) parameter (*)

( _ : sigexp ) anonymous parameter (*)

( spec ) signature as parameter (*)

¹) See the module syntax summary for a more precise grammar of structure expressions and functor application.

Signatures

sigexp ::= ...

longsigid signature identifier

( sigexp ) parentheses

( spec ) signature (*)

fct strpat -> sigexp functor

sigexp₁ -> sigexp₂ non-dependent functor ¹

¹) See the module syntax summary for a more precise grammar of functor signatures.

Specifications

spec ::= ...

exttype extdesc extensible datatype

constructor econdesc generative constructor

functor fundesc functor specification (*)

signature sigdesc signature specification

datdesc ::= tyvarseq tycon = <|> condesc <and datdesc> datatype description

extdesc ::= tyvarseq tycon extensible datatype

econdesc ::= <op> vid <of ty> : tyvarseq longtycon <and econdesc> new constructor