Power Programmierung/Power-Programmierung (Tewi)(1994).iso/j/dos/xenos.doc

Text File | 1992-10-24 | 15KB | 447 lines

Copyright (c) 1989 1990, Roger K.W. Hui & K.E. Iverson
Copyright (c) 1990-1992, Iverson Software Inc.
All Rights Reserved.


Roger Hui
1992 10 8


The !: Conjunction:

The !: conjunction currently takes integer scalar left and right
arguments, and derives verbs.  (One exception:  5!:0 is an adverb.)
These verbs behave like other verbs; in particular, they have intrinsic
ranks, may be assigned names, and may serve as arguments to adverbs and
conjunctions.  Where these verbs take names as arguments (file names,
WS names, or object names), the names are always boxed, and the verb
rank is 0.

As with all other verbs, verbs derived from !: requires one or two
arguments.  Some verbs have no "natural" arguments, but an argument
must nevertheless be supplied (and will be ignored in execution).
For example,
     6!:0 ''
  1991 6 6 10 50 23

NYA means not yet available.


0!:0      Host System Command
  The string argument is forwarded to the host system for
  execution, and the result is returned as a string with
  embedded new-lines.  For example: 0!:0 'dir *.exe'

0!:1      Spawn
  0!:1 forwards its string argument to the host system for execution,
  like 0!:0, but the output (if any) is ignored.  For example, 0!:1 can
  be used to invoke the vi editor on UNIX systems.

0!:2     Script

0!:3     Silent Script
  Script and Silent Script accept a boxed input file name as right
  argument and an optional boxed output file name as left argument.
  A boxed empty string right argument means "standard input", i.e.
  the keyboard.  The input file consists of lines of J sentences and
  other input lines, and is known as a "script".  The output file is
  suitable for subsequent use as a script.  Script differs from Silent
  Script in that it outputs to the "standard output" (the screen) as
  well as to any output file.  Examples:

  (<'sesslog') 0!:2 <''
    Input obtained from the keyboard; output appended to file
    "sesslog" and to the screen.

  0!:3 <'\jscripts\asdf'
    Input from file "\jscripts\asdf"; no output.  Input reverts
    to the keyboard at the end of "\jscripts\asdf".

  (<'outf') 0!:3 <'disk:folder:subfolder:inf'
    Input obtained from "disk:folder:subfolder:inf"; output
    appended to "outf".

  0!:2 <''
    Default.

  If there is a file named "profile.js" in the current directory,
  J will automatically execute 0!:2<'profile.js' at the start
  of a session.

0!:4      Lines

0!:5      Silent Lines
  Lines and Silent Lines are like Script and Silent Script, but the right
  argument is a string of lines separated by new-lines.

0!:55     Terminate Session
  0!:55 derives a verb which, when executed, terminates the session.

1!:0      Directory  NYA

1!:1      File Read
  The argument is a boxed file name; the result is a string
  of the file contents.  For example, 1!:1 <'dir\subdir\file.ext'
  The file name follows the conventions of the host system.
  The argument may also be the integer 1, meaning read from
  the keyboard.

1!:2      File Write
  xyz 1!:2 <':folder1:folder2:file'  writes string xyz to the
  specified file.  The right argument may also be the integer 2,
  meaning write to the screen.

1!:3      File Append
  string 1!:3 <'disk:folder1:folder2:file'

1!:4      File Size
  1!:4 'dir/file1';'file2';'phile3'

1!:11     Indexed File Read
  The argument is a 2-element list of boxes: a file name and
  a 2-element integer list of the index and length.  For example,
  1!:11 'test';5 20  reads 20 bytes from file "test", starting
  from position 5.  The index may be negative (the last byte of
  the file is index _1).  The length may be elided, whence the
  file is read from the index to the end of the file.

1!:12     Indexed File Write
  The right argument is a 2-element list of boxes: a file name
  and an integer index.  For example,  xyz 1!:12 'test';14
  writes (string) xyz to file "test", starting at position 14.
  The index may be negative (the last byte of the file is index _1).
  The positions to be written must already exist in the file (and the
  file must already exist).

1!:55     File Erase
  1!:55 <'careful'

2!:0      WS Name Class
  The integer result is the name class (see 4!:0) of the object
  named in the boxed left argument, in the workspace named in
  the boxed right argument.  In the following example, the
  result of the last sentence is 2 3 4.
    wsnc =. 2!:0
    save =. 2!:2
    noun =. i.3 4
    adv  =. /
    save <'wsname'
    ('noun'; 'save'; 'adv') wsnc <'wsname'

2!:1      WS Name List
  The sorted list of all names in the workspace named in the
  boxed right argument.

2!:2      WS Save
  Monad.  Save all global definitions into the workspace named
  in the boxed right argument.  The workspace is created if it
  does not already exist (and is overwritten if it already exists).

  Dyad.  Save the global definition of the object named in the
  boxed left argument into the workspace named in the boxed
  right argument.  If the object already exists in the saved
  workspace, it is overwritten; other objects in the saved
  workspace are unaltered.  The workspace is created if
  it does not already exist.

  Workspaces are currently in WSIS format (see 5!:3), but may
  use a different format in future J versions.  The workspace
  name follows the file naming rules of the host system.
  It'd be a good idea to devise your own naming convention to
  distinguish workspaces from other files.

2!:3      WS PSave   NYA
  "Protective" Save:  like Save, but the monad does not modify
  an existing workspace, and the dyad does not overwrite
  objects already in the saved workspace.

2!:4      WS Copy
  Copy the object named in the boxed left argument from the
  saved workspace named in the boxed right argument, and define
  it as a global object.  If the left argument is elided, all
  objects in the saved workspace are copied.

  Like all verbs, Copy applies to the argument cells in random
  order, so that if an object is copied from more than one
  workspace, the definition of the object could be from any of
  the workspaces.

2!:5      WS PCopy
  "Protective" Copy:  like Copy, but does not overwrite objects
  already defined.

2!:55     WS Erase
  Erase the object named in the boxed left argument, from the
  workspace named in the boxed right argument.

3!:0      Internal Type
  The internal "type" of a noun, where
  1  boolean
  2  literal
  4  integer
  8  floating point
  16 complex
  32 boxed
  64 box with key

3!:1      Convert to   Internal Representation
  A string of the internal representation of a noun.  The result
  is machine-dependent and may differ in different J versions.

3!:2      Convert from Internal Representation
  Inverse of 3!:1, but only nouns of type 2^i.5 are created.

4!:0      Name Class
  The argument is a boxed name; the result is its class:
  _1 other
  0  undefined, but valid name
  1  (not used)
  2  noun
  3  verb
  4  adverb
  5  conjunction

4!:1      Name List
  The argument is a subset of the integers from 2 to 5 (see 4!:0).
  The result is a list of boxed names belonging to the class(es)
  specified in the argument.  The optional left argument are initial
  letters of the names of interest.

4!:55     Erase
  The object named in the boxed argument is erased.

4!:56     Erase given name

5!:0      Fix
  5!:0 is an adverb which defines an object from its atomic or string
  representations.  For example,

     fx =. 5!:0
     ar =. 5!:1
     ((ar <'a') fx) -: a =. i. 3 4
  1
     plus =. +
     $$ ar <'plus'
  0
     2 ((ar <'plus') fx) 4 5
  6 7

  If the argument is a boxed list of boxes, it is assumed to be
  an atomic representation (a result of 5!:1).

  If the argument is a string, it is assumed to be a catenation
  of string representations (results of 5!:3).  The objects are
  defined, names embedded in the representation are assigned
  as a side effect, and the result of 5!:0 is the last
  represented object.

5!:1      Atomic Representation
  The argument is a boxed name; the result is a boxed list of
  two boxes uniquely representing the named object:

  noun:         id  value
  verb:         id  operator arguments
  adverb:       id  operator arguments
  conjunction:  id  operator arguments

  If an object is uniquely identified by the id alone (for example
  "a." or "+" or "/."), then the second field is elided, and the
  atomic representation is the id alone.

  Gerunds (results of the ` conjunction) are arrays of atomic
  representations.  5!:0 defines an object from its atomic
  representation.  Atomic representations are sometimes called
  "canonical" or "boxed" representations.

5!:2      Display Representation
  The argument is a boxed name; the result is the display representation
  of the named object.  5!:0 defines an object from its display
  representation.  (Different objects can have the same display
  representation, so 5!:0 is only a partial inverse.)
     f =. +/ . *
     f
  +-----+-+-+
  |+-+-+|.|*|
  ||+|/|| | |
  |+-+-+| | |
  +-----+-+-+
     each =. &. >
     (5!:2 <'f') -: (, each '+/') ; each '.*'
  1

5!:3      String Representation
  The argument is a boxed name; the result is a string of the WSIS
  (Workspace Interchange Standard) representation of the named object.
  5!:0 defines an object from its string representation.  See Section
  5.3 of "An Implementation of J" for details.

5!:4      Tree Representation
  The argument is a boxed name; the result is a literal table of the
  tree representation of the named object.  Box drawing characters
  (9!:6 and 9!:7) are used to draw the connecting lines in a tree.
  For example,
     nub =. (i.@# = i.~) # ]
     5!:4 <'nub'
               +- i.
         +- @ -+- #
    +----+- =
    |    +- ~ --- i.
  --+- #
    +- ]

5!:5      Linear Representation
  The argument is a boxed name; the result is a string which,
  when interpreted, produces the named object.  For example,
     nub =. (i.@# = i.~) # ]
     5!:5 <'nub'
  (i.@# = i.~) # ]
     $5!:5 <'nub'
  16
     a=.o.i.3 4
     5!:5 <'a'
  3.14159265358979323*i.3 4

6!:0      Time-Stamp
  The current time as a 6-element list: year, month, day, hour,
  minute, and second (including any fraction thereof).

6!:1      Time since session start

6!:2      Time required
  The string right argument is executed the number of times specified
  by the left argument (default: 1).  The execution results are discarded.
  The result of 6!:2 is the average number of seconds required for the
  execution.  For example:
     time=.6!:2
     time '+/i.10000'         NB. time to execute once
     10 time '+/i.10000'      NB. time to execute, averaged over 10 times

6!:3      Delay
  (6!:3) 60 [ 'sleep for a minute'

7!:0      Space currently in use

7!:1      Space used since session start

7!:2      Space required to execute an expression

8!:0      (PC only) Query CGA mode
  (8!:0 ''){'non-CGA mode'; 'CGA mode'

8!:1      (PC only) Set   CGA mode
  (8!:1) 0 [ 'set non-CGA mode'
  (8!:1) 1 [ 'set CGA mode'

8!:4      (PC only) Query screen attributes

8!:5      (PC only) Set   screen attributes
  The argument is a 4 by 2 matrix of integer values from 0 to 15.
  Attribute values are interpreted as follows:
  .---------------------------.
  | input area  | input area  |
  | background  | foreground  |
  |-------------+-------------|  0  black     4  red
  | output area | output area |  1  blue      5  magenta
  | background  | foreground  |  2  green     6  yellow
  |-------------+-------------|  3  cyan      7  white
  | cursor bar  | cursor bar  |
  | background  | foreground  |  8+i values in background specify "flashing";
  |-------------+-------------|  in foreground, "bright".
  | status line | status line |
  | background  | foreground  |
  |_____________|_____________|

8!:7      (PC only) Refresh screen
  Redisplay the contents of the screen.

8!:9      (PC only) Edit
  8!:9 y invokes the editor on y, a string with lines delimited
  by linefeeds (10{a.). Press F1 to get meanings of function keys.

8!:16     (Macintosh only) Query font attributes

8!:17     (Macintosh only) Set   font attributes
  Font attributes are a 3-element integer list of the font number,
  style, and size.  "Style" is the sum of one or more of the following
  integers, where
    1  Bold
    2  Italic
    4  Underline
    8  Outline
  Font attributes can also be set by the font dialog box, invoked
  by the "Font ..." item under the "Edit" menu.

8!:19     (Macintosh only) Print screen

9!:0      Query random link

9!:1      Set   random link.  Default: 16807

9!:2      Query display representation

9!:3      Set   display representation
  The argument is an integer vector of one or more representations
  to be used for default output of verbs, adverbs, and conjunctions.
    1  atomic (gerundial)
    2  display
    3  string
    4  tree
    5  linear

  For example:
     nub =. (i.@# = i.~) # ]
     nub
  +-------------------+-+-+
  |+--------+-+------+|#|]|
  ||+--+-+-+|=|+--+-+|| | |
  |||i.|@|#|| ||i.|~||| | |
  ||+--+-+-+| |+--+-+|| | |
  |+--------+-+------+| | |
  +-------------------+-+-+
     9!:3 (5 4)
     nub
  (i.@# = i.~) # ]
              +- i.
    +- @ -+- #
    +---+- =
    |   +- ~ --- i.
  --+- #
    +- ]

9!:4      Query prompt

9!:5      Set   prompt.  Default: '   '

9!:6      Query box drawing characters

9!:7      Set   box drawing characters
  The argument is an 11-element string of  nw,ts,ne, te,cr,tw,
  sw,tn,se, ns,ew  (northwest corner, tee south, northeast
  corner; tee east, etc.)  Defaults:

  [PC    ]  218 194 191  195 197 180  192 193 217  179 196 { a.
  [Others]  '+++++++++|-'

9!:8      Query error messages

9!:9      Set   error messages
  For example: Replace English messages (default) with French ones.

10!:k     Link to C function
  For LinkJ, 10!:k invokes the function jc(k,f1,f2).  You must modify
  jc() to assign values to f1 and f2 appropriate to k.  See Appendix C
  of "An Implementation of J" for details.

11!:0     (Windows only) Windows Driver
  See on-line help (press F1).

11!:1     (Windows only) Windows Visual Edit
  The WP string argument is amended via a visual editor.

128!:0    QR decomposition
  The QR decomposition of a complex matrix in the domain of %. .
  The result is an Hermitian matrix and a square upper triangular
  matrix, individually boxed.

128!:1    Invert a square upper triangular matrix