SML '97 Conversion Guide

1.1. Types and Type Checking

• 1.1.2. Type checking

  1.1.2.1. The value restriction
  1.1.2.2. Overloaded literals
  1.1.2.3 Defaulting overloads

• 1.1.3. Explicit type variable binding

• 1.1.4. Local datatypes

• 1.1.5. Datatype replication declarations

• 1.1.6. real not an equality type

• 1.2. Core Language

  • 1.2.1. Rebinding constructor names with val rec and fun

  • 1.2.2. Revised infix operator precedence rules

  • 1.2.3. Forbidden rebindings

  1.3. Modules

  • 1.3.1. Type definitions in signatures

  • 1.3.2. Datatype replication specs

  • 1.3.3. Adding definitions with where type

  • 1.3.4. Restriction of sharing to local paths

  • 1.3.5. Restriction of sharing to "formal" types

  • 1.3.6. Replacement of "definitional" sharing by definitional specs

  • 1.3.7. Structure sharing as derived form for type sharing

    • "weak" structure sharing
    • structures no longer have a unique static identity
    • sharing not "transitive" (or transitively inherited)

  • 1.3.8. include sigexp

  • 1.3.9. opaque signature matching (:>)

    • where can it be used
    • replaces "abstraction" declaration of SML/NJ

  • 1.3.10. equality type specs, inferred equality properties

  • 1.3.11. open and local specification forms deleted

  • 1.3.12. no repeated specifications of an identifier

  • 1.3.13. behavior of include (Defn vs SML/NJ)

• SML/NJ Deviations

  1. "val rec" syntax.
  2. more liberal withtype scoping rules

• SML/NJ Extensions

  1. Core

     1. or patterns
     2. vector patterns

  2. Modules

     1. higher-order functors
     2. structure definition specs
     3. where clause for structure definitions
     4. type spec merging with include

  Library and Environment Changes

  Probably the preponderance of the effort of porting code to SML '97 involves updating references to identifiers from the top level environment and other references to the built-in Basis library. The Basis Library is documented separately, but we will cover some highlights of the changes in this section.

  The SML/NJ Library has also been updated. New documentation for the SML/NJ Library is in preparation, but there is a SML/NJ Library Porting Guide that gives a module-level summary of the changes relative to the 0.3beta version of 1994. It lists name changes, deletions, and additions in the library relative to the 0.3beta release from 1994. This Porting Guide is also found in the smlnj-lib source directory in the file named PORTING. For documentation of the library signatures, see the comments in the source files for the various signature modules (e.g. src/smlnj-lib/Util/hash-table-sig.sml).

  For a concise summary of changes in the top level environment, see the Top Level Environment Comparison page.

  Basic Types

  Arithmetic

  • rem and quot not bound at top level, not infix
  • multiple precision of Int types (Int, LargeInt, Int31, Int32, [IntInf])
  • new word types, multiple precisions (word8, word31=word, word32)

  Characters and Strings

  A new character type has been added. Characters are no longer denoted by strings of length one. When you explode a string, you get a list of characters, not single character strings.

  Character Literals

  #"A"

  Functions explode and implode

  Character classifiers (e.g. isAlphaNum)

  Turning a character into a string, and vice versa

  Substrings

  Lists

  foldl, foldr replace fold, revfold, and their types are different from those of fold, revfold.

  A bunch of new functions.

  Some functions that were bound at top-level are not in SML '97. (exists)

  ListPair structure (zip, unzip, map, app)

  I/O

  TextIO

  outstream => TextIO.outstream
  instream  => TextIO.instream
  input     => TextIO.inputN
  output    => TextIO.output
  std_out   => TextIO.stdOut
  std_in    => TextIO.stdIn
  

  - TextIO.output(TextIO.stdOut, "abc\n");
  abc
  val it = () : unit
  - 
  

  print

  val print : string -> unit
  

  Not overloaded now. Still bound at top level.

    print 3  => print(Int.toString 3)
    print 3.0 => print(Real.toString 3.0)
  

  [see TextIO structure, IMPERATIVE_IO signature]

  System Facilities

  Invoking the compiler

  • use : string -> unit
    (bound in top level; alias for Compiler.Interact.useFile)
  • Compiler.Interact.useStream : TextIO.instream -> unit
    

  OS structure in Basis

  Posix structure in Basis

  SMLofNJ

  • exportML, heap image files, @SMLload command line parameter

    Question: Calling the function exportML, as in

    - SMLofNJ.exportML "image";
    

    creates a file called "image.mipseb-irix" that is not executable, while with SML/NJ 93 I would get an executable file called "image". I wonder if I am doing the export correctly or if there is a new procedure for using the exported image?

    Answer: The file "image.mipseb-irix" is a heap image -- not an executable. You can load it as follows:

    % sml @SMLload=image
    

    Note that you do not need to specify the ".mipseb-irix" suffix when specifying the image file, it will be inferred.

  Unix structure

  Useful control flags

  warning messages

  ---

  Dave MacQueen
  Last modified: Thu Mar 5 10:38:18 EST 1998