PDP-10 Maclisp

The ITS Lisp is called Maclisp, or PDP-10 Maclisp if necessary to disambiguate it against Multics Maclisp. Its direct ancestor is PDP-6 LISP.

The biggest difference between Multics Maclisp is PDP-10 version does not have “real” string data type, the PDP-10 Maclisp string is just a symbol with a special property been set. The good news is the format pretty printer function is still available to build strings with complex contents.

A sample MACLISP session on ITS using LEDIT MODE in EMACS LEDIT will work on both ITS and TOPS-20 ;tnx1.0e6 to GLS

    
    KA ITS 1648 DDT 1547 TTY 52               ;System herald
    
    :login smith                              ;The luser logs in
    
    :lisp                                     ;MACLISP is started
    
    LISP 2154                                 ;MACLISP version
    ALLOC? N                                  ;Take the world defaults
    
    (plus 3.14 2.71)                          ;Add two numbers
    5.85
    
    (car '(simple list))                      ;Return the CAR of a LIST
    SIMPLE
    
    (ledit)                                   ;Enters EMACS in LEDIT MODE
    
    (defun sum-squares (a b)                  ;Typed into the EMACS buffer
           (plus (times a a
                 (times b b))))               ;META-Z pushes DEFUN to the world
                                              ;CTRL-X Z returns to LISP
    
    ;READING FROM LEDIT SUN-SQUARES           ;Back in LISP
    ;EDIT COMPLETED
    
    (sum-squares 2.0 3.0)                     ;call SUM-SQUARES
    36.0                                      ;Returns the wrong number
    
    (ledit)                                   ;Re-enter EMACS in LEDIT MODE
    
    CTRL-S (times a a                         ;Typed into EMACS
                                              ;Search for STRING (times a a
    
    (defun sum-squares (a b)                  ;Correct SUM-SQUARES
           (plus (times a a)
                 (times b b)))                ;META-Z pushes new DEFUN to world
                                              ;CTRL-X Z returns to LISP
    
    ;READING FROM LEDIT SUM-SQUARES           ;Back in LISP
    ;EDIT COMPLETED
    
    (sum-squares 2.0 3.0)                     ;Call SUM-SQUARES again
    13.0                                      ;Correct result

The LISP … Editor … LISP … loop will no doubt be repeated many times.

HELLO WORLD and LOOP examples

   @maclisp                        ; start MACLISP at the TOPS-20 EXEC
   
   LISP 2122                       ; MACLISP Version 2122
   Alloc? n                        ; take the defaults
   
   
   * 
   (defun HELLO ()                 ; DEFINE FUNCTION "HELLO"
   (princ "Hello World!"))         ; print characters "Hello World!"
   HELLO                           ; MACLISP reports a definition for the function "HELLO"
   (hello)Hello World!             ; The function "HELLO" is called and "Hello World!" is printed
   T                               ; MACLISP reports T for a successful function call

   @maclisp
   
   LISP 2122
   Alloc? n
   
   
   *
   (loop for x in '(a b c d e)     ; Call the macro "LOOP" for VARIABLE "x" in a list of "a b c d e"
   do (print x))                   ; DO a PRINT of the value of "x"
   ;Loading LOOP 725               ; MACLISP loads LOOP version 725
   ;Loading DEFMAX 98              ; MACLISP loads DEFMAX version 98
   A                               ; 1. X = A
   B                               ; 2. X = B
   C                               ; 3. X = C
   D                               ; 4. X = D
   E                               ; 5. X = E 
   NIL                             ; DO called PRINT X which returned NIL because there was nothing
                                   ; left to PRINT in the list of "a b c d e"

MATH examples

   @maclisp
   
   LISP 2122
   Alloc? n
   
   
   *     
   (+ 2 2)
   4
   (- 2 2)
   0
   (* 2 2)
   4