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Annotation of 43BSD/contrib/apl/doc/man.4, revision 1.1

1.1     ! root        1: .NH 1
        !             2: Editing Functions
        !             3: .PP
        !             4: Function editing on
        !             5: \*u \*a
        !             6: differs from that on other
        !             7: \*a systems.
        !             8: The ``del'' character is not used.
        !             9: Instead,
        !            10: the \*u editor
        !            11: is used.
        !            12: There are two alternatives.
        !            13: .PP
        !            14: The ``)editf'' system command is
        !            15: used to edit a function residing
        !            16: in the internal workspace.
        !            17: The command
        !            18: .sp
        !            19:        )editf fn
        !            20: .sp
        !            21: writes the function ``fn'' into
        !            22: a temporary file and calls
        !            23: the editor to process it.
        !            24: When the editor is finished,
        !            25: \*a reads it back in.
        !            26: .PP
        !            27: The command:
        !            28: .sp
        !            29:        )edit junk
        !            30: .sp
        !            31: invokes the editor to process
        !            32: the \*u file ``junk''.
        !            33: When the editor is terminated
        !            34: via the ``q'' command,
        !            35: control returns to \*a,
        !            36: which will read ``junk'' into
        !            37: the internal workspace.
        !            38: Note that
        !            39: this method involves files
        !            40: external to \*a.
        !            41: ``)editf'' is generally a better choice
        !            42: since it allows all information relating
        !            43: to the workspace to be contained
        !            44: within the workspace.
        !            45: .PP
        !            46: Because of the way in which editing
        !            47: is performed,
        !            48: there are two points which need
        !            49: special attention.
        !            50: First,
        !            51: it is not possible to edit a suspended
        !            52: function.
        !            53: (For a description of suspended functions
        !            54: and how to reset them,
        !            55: see ``The State Indicator''.)
        !            56: Second,
        !            57: if the function header
        !            58: (first line of the function)
        !            59: contains a syntax error,
        !            60: \*a will
        !            61: .I not
        !            62: read in the function.
        !            63: In general,
        !            64: this means that the function
        !            65: is no longer defined in the
        !            66: workspace,
        !            67: and the only other copy
        !            68: exists in a temporary file.
        !            69: In order to save you a lot
        !            70: of work retyping,
        !            71: \*a will
        !            72: automatically copy the temporary
        !            73: file into a file called
        !            74: ``apl.badfn''
        !            75: .PP
        !            76: An example is probably called for at
        !            77: this point
        !            78: to clear the mud somewhat.
        !            79: The following shows the creation
        !            80: of the function ``fact''
        !            81: which computes factorials
        !            82: by multiplication.
        !            83: .DS
        !            84:        )editf fact
        !            85:        [new fn]
        !            86: XED
        !            87: 0 lines
        !            88: >a
        !            89: [ 0 ]  n { fact+i
        !            90: [ 1 ]    n { 1
        !            91: [ 2 ]  loop: } (i = 0) / 0
        !            92: [ 3 ]    n { n X i
        !            93: [ 4 ]    i { i - 1
        !            94: [ 5 ]    } loop
        !            95: [ 6 ]  .
        !            96: >w
        !            97: >q
        !            98: n { fact+i
        !            99:       ^
        !           100: syntax error
        !           101: Function saved in apl.badfn
        !           102: .DE
        !           103: The error in line 0
        !           104: (``fact+i'')
        !           105: caused \*a to stop reading
        !           106: the function,
        !           107: so it was automatically copied
        !           108: to the file ``apl.badfn''.
        !           109: To get it back,
        !           110: you can say:
        !           111: .DS
        !           112:        )editf fact
        !           113:        [new fn]
        !           114: XED
        !           115: 0 lines
        !           116: >r apl.badfn
        !           117: 5 lines
        !           118: >0s/+/ /p
        !           119: [ 0 ]  n { fact i
        !           120: >w
        !           121: >q
        !           122: .DE
        !           123: .PP
        !           124: If you use ``)edit'' instead of ``)editf'',
        !           125: \*a will not worry about saving
        !           126: the function in ``apl.badfn''
        !           127: because you were editing from a
        !           128: \*u file rather than
        !           129: the internal workspace,
        !           130: and that file still exists.

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