The following is an annotated transcript of an Interlisp session run on TWENEX. It is adapted from the example session in Interlisp Reference Manual* pages 2.5-2.9.
User input is shown in WHITE.
@INTERLISP:LISP
INTERLISP-10 31-Dec-84 ...
Hello.
|
The user calls Interlisp from EXEC. Interlisp prints a date, and a greeting. The prompt character "_" indicates the user is at the top level of Interlisp. |
3_DEFINEQ((FACT (LAMBDDA (N) (IF N=0 THEN NIL ELSE N*(FACTT N-1]
(FACT)
|
The user defines the function, fact, for computing
the factorial of n. The function definition uses CLISP
(Conversational Lisp; IF N=0 THEN NIL
ELSE...). The CLISP will automatically be converted to
Lisp when the function is run. The function definition
contains three errors. |
4_(GETD 'FACT)
(LAMBDDA (N) (IF N=0 THEN NIL ELSE N* (FACTT N-1)))
|
The user "looks" at the function definition. Note that the
user typed an input consisting of a single expression,
i.e., (GETD (QUOTE FACT)), which was therefore
interpreted as a form for eval. The user could also have
typed GETD(FACT). |
5_FACT(3) LAMBDDA {below FACT} -> LAMBDA ? Yes FACTT {in FACT} -> FACT ? Yes |
The user runs his function. Two errors and corrections are offered by DWIM. In each case, the user indicats his approval by typing "Y", DWIM makes the correction, i.e., actually changes the definition of fact, and then continues the computation. |
NON-NUMERIC ARG
NIL
(ITIMES broken)
|
An error occurs that DWIM cannot handle and the system goes into a break. At this point, the user can type in expressions to be eval-ed or apply-ed exactly as at the top level. The prompt character ":" indicates that the user is in a break, i.e., that the context of his computation is available. In other words, the system is actually "within" or "below" the call to itimes in which the error occurred. |
6:BT
ITIMES
COND
FACT
COND
FACT
COND
*ENV*
FACT
*ENV*
APPLY
*PROG*LAM
LISPX
ERRORSET
EVALQT
NIL
|
The user types in the break command, BT, which
calls for a backtrace to be printed. |
7:N
1
|
The user asks for the value of the variable n, i.e.,
the most recent value, or binding. The interpreter will search
the stack for the most recent binding, and failing to find one,
will obtain the top level value from the atoms's value cell,
which is car of the atom. If there are no bindings, and
the value cell contains the atom NOBIND, and
unbound atom error is generated. |
8:EDITF(FACT)
edit
|
The user realizes his error, and calls the editor to fix it. It is an extremely useful facility of Interlisp. |
1*(R NIL 1)
|
The user instructs the editor to replace
all NIL's (in this case there is only one) by
1. The editor physically changes the expression it is operating
on so when the user exits from the editor, his function, as
it is now being interpreted, has been changed. |
2*OK
FACT
|
The user exits from the editor and returns to the break. |
9:RETURN 1
ITIMES = 1
6
|
The user specifies the value to be used by itimes in
place of NIL by using the break
command RETURN. This causes the computation to
continue, and 6 is ultimately returned as the value of the
original input, fact(3). |
10_PP FACT
(FACT
[LAMBDA (N) **COMMENT**
(if (ZEROP N)
then 1
else (ITIMES N (FACT (SUB1 N])
(FACT)
|
The user prettyprints fact, i.e., asks it be printed with appropriate indentations to indicate structure. Prettyprint also provides a comment facility. Note that both the changes made to fact by the editor and those made by DWIM are in evidence. |
11_MAKEFILES() ****NOTE: the following are not contained on any file: the functions: FACT want to say where the above go ? Yes (functions) FACT File name: FACT.LISP create new file FACT.LISP ? Yes FACT.LISP... (<PAPA>FACT.LISP.1) |
The user calls makefiles to write out any changes he
has made. The file package knows that the function fact
has been changed, but doesn't know on which file it belongs,
and asks the users as shown in the example. After this
interaction, the symbolic
file <PAPA>FACT.LISP.1 is written out. This
file can be loaded into Interlisp at a later date via the
function load, will cause fact to be defined as
it currently is. There is also a facility in Interlisp for
saving and restoring an entire core image via the
funcitons sysout and sysin. |
13_LOGOUT()
@
|
The user logs out, returning control to EXEC. However, he
can still continue his session by re-entering Interlisp via the
EXEC CONTINUE command. |
* Warren Teitelman. Interlisp Reference Manual. (1978). Accessed: October 6, 2024. [Online]. Available: https://www.softwarepreservation.org/projects/LISP/interlisp/Interlisp-Oct_1978.pdf