1 03/23/79   Incompatibilities relative to VS APL
 2 
 3 
 4      This document lists the known incompatibilities between Multics APL and
 5 IBM VS APL.  The relevant manuals are "Multics APL", Order No. AK95-1, and "APL
 6 Language", GC26-3847-4.  This list is subject to revision.
 7 
 8 1.  Anything that is undefined by the APL language may be different, such as
 9     the exact order of evaluation.  Multics APL uses the same basic
10     right-to-left order of evaluation as VS APL.
11 
12 2.  The minimum and maximum identities and the range of the )DIGITS command
13     change as indicated in the following table:
14               VS APL                                                Multics APL
15       min     7.237005577332262e75                       1.70141183460492317e38
16       max    ^7.237005577332262e75                      ^1.70141183460492317e38
17       digits  1 - 16                                                     1 - 19
18     Multics APL numbers have a larger mantissa and a smaller exponent than
19     numbers on VS APL.
20 
21 3.  The comparison tolerance algorithm differs slightly between Multics APL and
22     VS APL.  Multics APL considers two numbers A and B are equal within fuzz if
23     the following relation is true:  (|A-B) <^H_ qCTx|A-B.  Multics APL considers
24     the value of C to be the integer fC+0.5 if (|C-fC+0.5) < qIT, where qIT is
25     the integer tolerance.
26 
27 4.  The Multics APL random number operators (monadic and dyadic ?) are
28     identical to the VS APL operators for values <^1+2*31.
29 
30 5.  The following VS APL commands are mapped into their Multics equivalents:
31               )MSG     send_message
32               )MSG ON  immediate_messages
33               )MSG OFF defer_messages
34     The following VS APL commands are unavailable in Multics APL: )OPR, )QUOTA,
35     )STACK, and )WSSIZE.
36 
37 6.  The Multics login protocol is different.  Multics users are denoted by a
38     name, not a number.  Multics APL is available both as a normal Multics
39     command and as a special subsystem that confines the user to the APL
40     environment.
41 
42 7.  The automatic saving of the CONTINUE workspace when a user's console is
43     hung up is not available.
44 
45 8.  The error marker is placed differently in some cases.  Multics APL detects
46     some errors during function definition instead of during execution.
47 
48 9.  The saving of workspaces is limited by the user's Multics disk record
49     quota, instead of by the number of workspaces.
50 
51 10. Multics APL handles the ATTN key (also called LINE BREAK or QUIT) slightly
52     differently.  The ATTN key may be used for editing input and interrupting
53     the APL interpreter.
54 
55     Typing mistakes may be corrected by backspacing and pressing the ATTN key;
56     APL will type the editing prompt character: "v".  As in VS APL, the
57     LINEFEED key may also be used.
58 
59     The interpreter may be interrupted by pressing the ATTN key twice (or once,
60     if no typed input is available to edit).  APL will type a new-line
61     character in response to an interrupt-type ATTN.  Either overstruck O U T
62     or an interrupt-type ATTN may be used as an escape from '^Hq (quad-quote)
63     input.
64 
65     Multics APL usually interrupts between lines;  however, long computations
66     may be interrupted within a line.  In any case, the error marker accurately
67     shows the point of interruption.  Multics APL always restarts at the
68     beginning of a line.
69 
70 11. The following errors cannot occur in Multics APL:  ENTRY, q-- IMPLICIT,
71     INTERFACE QUOTA EXHAUSTED, NO SHARES, RESEND, SYMBOL TABLE FULL, and STACK
72     FULL.  The following errors can occur in Multics APL but not in VS APL:
73     CONTEXT, RESULT SIZE, NONCE, COMPATIBILITY, DEPTH, INTERRUPT, USAGE, FILE
74     TIED, FILE TIE ERROR, FILE INDEX, BAD FILE, OLD FILE, FILE NAME, FILE TIE
75     QUOTA, FILE ACCESS, BAD ACCESS MATRIX.
76 
77 12. The qAV (atomic vector) system variable has been renamed to qCS (character
78     set) to emphasize that the Multics APL character set is different from that
79     of VS APL.
80 
81 13. The qHT (horizontal tab) system variable is not available in Multics APL.
82     By default, tabs are assumed to be set every ten spaces (the normal Multics
83     convention).  The )TABS system command may be used to change this to any
84     other number.
85 
86 14. The )SINL command is not available in Multics APL.  Use )SIV.
87 
88 15. The qTC (terminal control) system variable is not available in Multics APL.
89     Use qCS.
90 
91 16. Multics APL does not support the 3270 terminal.
92 
93 17. VS APL implements a file system using shared variables.  Multics APL does
94     not provide shared variables, but does provide a set of system functions
95     that implement a full APL file system, similar to the Scientific
96     Timesharing Corp.  or I. P. Sharp Associates Ltd. file systems.