1 4/11/79 - Multics Emacs PL/I mode
2
3 **This file is intended to be perused via dprint, print, or via an**
4 **editor. It is not intended to be perused with the help command **
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6
7
8
9 ^L
10 PL/I mode provides an automatic assistance in PL/I progam formatting in the
11 real-time editing context of Multics EMACS. The basic facility provided at
12 this time is that of lining up untyped PL/I statements, although on a
13 one-for-one basis it will line up typed ones, too.
14
15 Enter PL/I mode by issueing ESC-Xpl1-mode. It will take a couple of
16 seconds to "load itself". When in PL/I mode, which shows up on the Mode line
17 as "PL/I" as a major mode, the following non-default key bindings apply:
18
19 TAB ^I Indent this PL/I statement properly if not yet
20 typed in tab out to it; otherwise readjust its
21 indentation properly.
22 ESC-CR ESC-^M Like CR and TAB.
23 ESC-^C Compile buffer. Write this buffer to its default pathname
24 and compile it, using the compiler "pl1" and assuming
25 "-tb" for options. These may be changed with the
26 extended commands set-compiler and set-compile-options.
27 Highly effective in two-window mode.
28 See fortran-mode.info for more on this.
29 ESC-^D Try to find a declaration for the entry-point whose
30 name is to the left of the cursor, and insert it.
31 There exists a library of such.
32 If the declaration is not in the library,
33 ESC-^D will attempt to figure it out from inbound
34 parameter descriptors in an object segment
35 responding to that name.
36 error_table_$xxx can be declared by ESC-^D, too.
37 ESC-^H ESC-Backspace Delete 5 columns of indentation.
38 Intended for undenting END's.
39 ESC-^I ESC-TAB Add 5 columns of indentation.
40 Intended for asserting your own style.
41 ^X^D Control X-Control D Find next error. When used after
42 an ESC-^C, will search for errors and place the cursor
43 on them in the source. Highly effective in two window
44 mode. See fortran-mode.info for more information on
45 the compilation error facility.
46 ^XC Control X-C Start or end a comment. Text following
47 this will be set off as a comment. A second ^XC ends
48 the comment.
49
50 All the standard commentation commands ESC-; etc. do the PL/I
51 thing. Word commands ESC-F etc. in PL/I mode buffers consider
52 the dollar sign to be part of a word.
53
54 The indentation rules which are followed are such:
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56 Any fragment of an incomplete statement gets lined up 5 after the
57 start of that statement. The statement after a DO or BEGIN gets indented 5
58 times one less than the number of IF's in the DO or BEGIN. In "inding style
59 2", the statement after an END gets lined up 5 LESS than the END statement;
60 the first statement in a program gets lined up at col. 11 Multics
61 reckoning. OTHERWISE, each statement lines up with the previous one.
62
63 There are two styles available; the default is 1, you can get 2 by saying
64 ESC-Xopt pl1-inding-style 2 CR
65
66 i.e. it is managed by the EMACS option mechanism.
67
68 In style 1, you get;
69
70 if x = 6 then do;
71 bar = 5;
72 foo = 6;
73 end;
74
75 In style 1, you are expected to line the END up yourself use ESC-^H because
76 it is impossible in realtime to predict that an untyped statement is going to
77 be an END. You must undent the end yourself, because the next statement will
78 line up with it.
79
80 In style 2 you get
81
82 if x = 6 then do;
83 bar = 5;
84 foo = 4;
85 end;
86 next = 17;
87
88 Obviously, emacs is happier with this, because it can figure out the next
89 statement after the END once you have typed it.
90
91 There are no known bugs in the mode's PL/I parsing: it pretentiously
92 claims to be able to parse any legal PL/I statement, with the following
93 exception: Multi-dimensional label constants not supported not a big
94 problem multics PL/I doesnt support them either.
95
96 There is also a minor mode called "electric PL/I mode", which can be
97 obtained by ESC-Xelectric-modeCR once in PL/I mode, or ESC-X electric-pl1-mode
98 CR. To get it by default as your mode for PL/I programs, put the statement
99
100 defprop pl1 electric-pl1-mode suffix-mode
101
102 in your start_up.emacs. Some users have found electric PL/I mode overly
103 violent, so it remains an option. It connects semicolon to a function which
104 automatically indents for the next statement after inserting a semicolon; use
105 \; to get a semi in without the electric action. Also, this action is
106 suppressed if there is a next line, and it is not empty. The "electric
107 semicolon" also moves "end"'s back for you in inding-style 1, when you type
108 the ";" of the "end" statement. Be careful to "\" ;'s in strings there are
109 problems there. Electric PL/I mode also gives ":" electric action, i.e.,
110 indenting after labels.