From ef373cb4047e51381819b1ffe5385fa8d2edcc7f Mon Sep 17 00:00:00 2001
From: Jacques Comeaux <jacquesrcomeaux@gmail.com>
Date: Sat, 20 Aug 2022 15:57:06 -0500
Subject: Add S-Exp printer

---
 print.s | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 62 insertions(+), 11 deletions(-)

(limited to 'print.s')

diff --git a/print.s b/print.s
index f84ca70..3955d56 100644
--- a/print.s
+++ b/print.s
@@ -1,11 +1,62 @@
-  MOV R1, -(SP)
-  BR 20$
-10$:
-  TSTB @#177564
-  BEQ 10$
-  MOVB R1, @#177566
-20$:
-  MOVB (R0)+, R1
-  BNE 10$
-  MOV (SP)+, R1
-  RTS PC
+print:
+004000 012705 MOV #6000, R5         ; store print buffer address in R5
+004002 006000
+004004 032700 BIT #1, R0            ; test if sexp is cons or atom
+004006 000001
+004010 001003 BNE 6
+004012 004727 JSR PC, #handle_cons
+004014 004100
+004016 000402 BR 4
+004020 004727 JSR PC, #handle_atom
+004022 004200
+004024 012725 MOV #"\n\0", (R5)+    ; move newline and null byte into print buffer
+004026 000012
+004030 000127 JMP #print_buffer
+004032 004300
+
+handle_cons:
+004100 016046 MOV 2(R0), -(SP)      ; push cdr onto stack
+004102 000002
+004104 011000 MOV @R0, R0           ; traverse to car
+004106 032700 BIT #1, R0            ; test if car is cons or atom
+004110 000001
+004112 001005 BNE 12
+004114 112725 MOVB #"(", (R5)+      ; if cons output open paren
+004116 000050
+004120 004727 JSR PC, #handle_cons  ; recurse
+004122 004100
+004124 000402 BR 4
+004126 004727 JSR PC, #handle_atom  ; if atom output atom
+004130 004200
+004132 012600 MOV (SP)+, R0         ; pop cdr from stack
+004134 032700 BIT #1, R0            ; test if cdr is cons or atom
+004136 001005 BNE 12
+004140 112725 MOVB #" ", (R5)+      ; if cons output space
+004142 000040
+004144 004727 JSR PC, #handle_cons  ; recurse
+004156 004100
+004150 000402 BR 4
+004152 112725 MOVB #")", (R5)+      ; if atom output close paren
+004154 000051
+004156 000207 RTS PC
+
+handle_atom:
+004200 000401 BR 2            ;
+004202 110125 MOVB R1, (R5)+  ; move char to print buffer
+004204 112001 MOVB (R0)+, R1  ; get next byte
+004206 001372 BNE -6          ; if not null continue
+004210 000207 RTS PC          ;
+
+print_buffer:
+004300 012705 MOV #6000, R5       ; restore print buffer pointer
+004302 006000
+004304 000404 BR 12
+004306 105737 TSTB @#177564       ; test if console ready
+004310 177564
+004312 001772 BEQ -6              ; loop while not ready
+004314 110137 MOVB R1, @#177566   ; send char to console
+004316 177566
+004320 112501 MOVB (R5)+, R1      ; get next byte
+004322 001362 BNE -16             ; if not null continue
+004324 000127 JMP #read (002000)
+004326 002000
-- 
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