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 GOFER(1)                                                           GOFER(1)




 NAME
      gofer, gofc - Gofer programming language interpreter and compiler


 SYNOPSIS
      gofer

      gofc [file] ...


 DESCRIPTION
      Gofer is an interactive functional programming environment (i.e. an
      interpreter) supporting a language based on the draft report for
      Haskell version 1.2, including the following features:
        o  Lazy functional language features such as
                lazy evaluation, higher order functions, pattern matching,
                etc.
        o  Wide range of built-in types
                with provision for defining new free datatypes and type
                synonyms.
        o  Polymorphic type system
                with provision for overloading based on a system of type
                classes.
        o  Full Haskell 1.2 expression and pattern syntax
                including lambda, case, conditional and let expressions,
                list comprehensions, operator sections, and wildcard, as and
                irrefutable patterns.
        o  Partial implementation of Haskell 1.2 I/O
                enabling the use of simple interactive programs and programs
                reading and writing text files.
        o  Constructor classes and overloaded monad comprehensions.
        o  Simple minded compiler/translator gofc
                with runtime system for generation of standalone
                applications.
        o  Runs on PC compatible computers,
                but also works on Sun and other workstations.
      Gofer is intended as an experimental language, particularly where type
      classes are involved.  Gofer extends the Haskell type class system in
      several ways:
        o  Type classes with multiple parameters.
        o  Instances of type classes
           may be defined non-overlapping, but otherwise arbitrary types.
        o  Predicates in contexts
           may involve arbitrary type expressions, not just type variables
           as in Haskell.
        o  Basic approach to dictionary construction is different,
           based on the approach described in a posting to the Haskell
           mailing list early in Feburary 1991.  The resulting system
           ensures that all dictionaries are constructed before evaluation
           begins, avoiding repeated construction and enabling the shared
           evaluation of overloaded constants in dictionaries.



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 GOFER(1)                                                           GOFER(1)




      The most significant features of Haskell not currently supported are:
      modules, arrays, overloaded numeric constants, default declarations,
      derived instances, contexts in datatype definitions.

 INTERPRETER
      The Gofer interpreter is usually entered by giving the command
      `gofer'.
      Most commands in Gofer take the form of a colon followed by one or
      more characters which distinguish one command from another.  There
      are  two commands which are particularly worth remembering:
        o  :q  exits the  Gofer  interpreter.
           On most systems, you can also exit from Gofer by typing the end
           of  file  character (^D).
        o  :?  prints a list of all the commands,
           which can be useful if you forget the name of the command that
           you want to use.
      Note that the interrupt key (^C on most systems) can  be  used  at
      any time whilst using Gofer to abandon the process of reading in a
      file  of function definitions or the evaluation  of  an  expression.
      When  the interrupt key is detected, Gofer prints the string
      "{Interrupted!}" and prints the "? " prompt so that further commands
      can be entered.

 COMPILER
      Compiling a program with gofc is very much like starting up the Gofer
      interpreter.  The compiler starts by reading the prelude and then
      loads the script files specified by the command line.  These scripts
      must contain a definition for the value main :: Dialogue which will be
      the dialogue expression that is evaluated when the compiled program is
      executed.
      For example, if the file apr1.gs contains the simple program:
            main :: Dialogue
            main  = appendChan "stdout" "Hello, world\n" exit done
      then this can be compiled with the following command.
            gofc apr1.gs
      The output is written to the file apr1.c -- i.e. the name obtained by
      removing the .gs suffix and replacing it with a .c suffix.  Other
      filename suffixes that are treated in a similar way are:
            .prj    .gp              for Gofer project files
            .prelude                 for Gofer prelude files
            .gof    .gs              for Gofer scripts
            .has    .hs              for Haskell scripts
            .lhs    .lit             for literate scripts
            .lgs    .verb
      If no recognized suffix is found then the name of the output file is
      obtained simply by appending the .c suffix to the input name.  Be
      careful; if you take an input file called `prog' and compile it to
      `prog.c' using gofc, make sure that you do not compile the C program
      in such a way that the output is also called `prog' since this will
      overwrite your original source code!  For this reason, you should
      always using file extensions such as .gs if you are using gofc.



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 GOFER(1)                                                           GOFER(1)




      If you run gofc with multiple script files, then the name of the
      output file is based on the last script file to be loaded.  For
      example, the command `gofc prog1.gs prog2.gs' produces an output file
      `prog2.c'.
      The compiler gofc also works with project files, using the name of the
      project file to determine the name of the output file.  For example,
      the miniProlog interpreter can be compiled using:
            gofc + miniProlog.prj
      You can also specify Gofer command line options as part of the command
      line used to run gofc.  Think of it like this; use exactly the same
      command line to start Gofc as you would have done to start Gofer (ok,
      replacing the command `gofer' with `gofc') so that you could start
      your program immediately by evaluating the main expression.

 FILES
      The files in /usr/local/lib/Gofer/lib contain various preludes and
      header files for the Gofer compiler.

 SEE ALSO
      Documentation about how to run the system is in the directory
            /usr/local/lib/Gofer/docs
      For starters see the file ch03 in that directory.  See the file
      release.228 in that directory for more about the compiler.
      sml(1)

 AUTHOR
      Gofer was written by Mark P. Jones and has benefited greatly from
      suggestions, comments and bug reports from its users.  This manual
      page was prepared by Gary Leavens.

























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