HELP COMMANDS                              Simon Nichols, September 1987
                                           Revised R. Duncan, March 1990

Top-level commands in PML.


         CONTENTS - (Use <ENTER> g to access required sections)

  1   Introduction

  2   Available Commands

  3   Invoking Commands From Ved


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1  Introduction
-----------------------------------------------------------------------

In addition to evaluating declarations  and expressions in the  Standard
ML language, the top level of the PML system accepts a range of commands
which give access to features of the Poplog environment.

Commands are valid only at the very top level of PML, wherever a  topdec
would be valid in  the standard language. The  syntax of commands is  as
follows:

    command ::=
        name arg-1 __ arg-n << ";" >>       (n >= 0)

A command name  is a standard  short identifier. Command  names are  not
reserved: they  may be  reused freely  as normal  identifiers. The  only
possibility of confusion arises where such an identifier is used as  the
name of a variable, constructor or exception occurring as the first item
in a  top-level  expression.  In  this case  the  identifier  should  be
enclosed in parentheses to prevent its interpretation as a command name.

A command argument may be a standard string constant or, if not  quoted,
any arbitrary sequence of printing characters excluding the  separators:
space, tab, newline,  semicolon (;)  and string quote  ("). An  unquoted
argument need not conform to the standard lexical rules.

A command is terminated by the end of line or by a semicolon,  whichever
comes first; a command may not extend over more than one line.

Examples of valid commands:

    cd

    cd ../example

    cd "../example";


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2  Available Commands
-----------------------------------------------------------------------

The following commands are recognised by PML. Command names are shown in
bold type, and arguments in italic. For most commands, the arguments are
optional.


bye
    Exits  from  PML.  This  is  equivalent  to  calling  the   function
    System.exit. See HELP * exit.


cd directory-name
    Changes the current working (default) directory to that given, or to
    the home  (login) directory  if  the argument  is omitted.  See  pwd
    below.


help topic
    Displays documentation on the given topic.  The topic may be any  of
    those listed in the file HELP * HELPFILES or else the name of a  PML
    system or library identifier. If no topic is given, an  introductory
    help file is displayed.


im filename
    Invokes the editor in  ``immediate mode'' on the  named file; if  no
    filename is  specified, the  last immediate-mode  filename is  used.
    Immediate mode is a way of interacting with the PML system inside an
    editor buffer. See HELP * IM, * MLVED


load filename
    Compiles the named file as an SML program; if no filename is  given,
    the most-recently referenced  filename is used.  See HELP * COMPILE
    for full details.


pop11
    Switches from ML to  the language Pop-11. To  return to ML, use  the
    Pop-11 macro pml.


pwd
    Prints the current  working (default) directory.  All filenames,  if
    not given as absolute pathnames, are interpreted relative to this.


showdef identifier ...
    Displays  information  about  identifiers  defined  in  the  current
    environment. See HELP * SHOWDEF for details.


showlib filename
    Displays the  program file  which  would be  compiled if  the  given
    filename were used as an argument to load.


teach topic
    Displays teaching  documentation  on  the  given  topic.  There  are
    currently no  PML-specific  TEACH files,  but  some of  the  general
    Poplog files (on Ved, for example) may be of interest to new  users.
    If invoked without a parameter, the file TEACH * TEACH is  displayed
    which gives a simple introduction to using Ved and Pop-11.


trace identifier ...
untrace identifier ...
    Start and stop tracing the named functions. See HELP * TRACE.


ved filename
    Invokes the Poplog editor, Ved, on the given file; if no filename is
    given,  the   most-recently  referenced   filename  is   used.   See
    HELP * MLVED


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3  Invoking Commands From Ved
-----------------------------------------------------------------------

All these commands are available from inside Ved too: press the  <ENTER>
key to get to the command line and type the command as you would to  the
PML top-level.

Example:

    <ENTER> help mlved

    <ENTER> showdef +

Output produced  by commands  is  sometimes presented  differently  when
called from inside Ved.

Other commands available from Ved are described in HELP * MLVED.


--- C.all/pml/help/commands
--- Copyright University of Sussex 1994. All rights reserved.
