games/mix: document -g option, rename tests to examples as it is in the man page

sys/man/1/mix

@@ -6,6 +6,9 @@ assembler and emulator
 .SH SYNOPSIS
 .B games/mix
 [
+.B -g
+]
+[
 .I file ...
 ]
 .SH DESCRIPTION
@@ -18,7 +21,11 @@ architecture. The command assembles the named
 files into memory and then presents a command
 prompt to control an emulated
 .B MIX
-machine.
+machine. The
+.B -g
+option causes the emulator immediately to run a complete assembled
+.B MIX
+program and exits the emulator when the emulator halts. 
 .PP
 The following commands are accepted:
 .TP

sys/src/games/mix/examples/maximum.m

@@ -0,0 +1,14 @@
+# Entry condition R1 = n.
+# Exit: RA = max R2 = index of max in X
+X	EQU	1000
+ORIG	3000
+MAXIMUM	STJ	EXIT	# Subroutine linkage.
+INIT	ENT3	0,1	# M1. Initialize k ← n.
+	JMP	CHANGEM	# j ← n, m ← X[n], k ← n-1.
+LOOP	CMPA	X,3	# M3. Compare.
+	JGE	*+3	# To M5 if m ≥ X[k].
+CHANGEM	ENT2	0,3	# M4. Change m. j ← k.
+	LDA	X,3	# m ← X[k].
+	DEC3	1	# M5. Decrease k.
+	J3P	LOOP	# M2. All tested? To M3 if k > 0.
+EXIT	JMP	*	# Return to main program.

sys/src/games/mix/examples/maxmain.m

@@ -0,0 +1,25 @@
+	ORIG	X
+	CON	0
+	CON	3910
+	CON	23
+	CON	-45
+	CON	310
+	CON	475
+	CON	40291
+	CON	358
+	CON	20912
+RESULT	ALF	"MAX: "
+	CON	0
+	ALF	" AT: "
+	CON	0
+	ORIG	EXIT+1
+MAIN	ENT1	RESULT-X-1
+	JMP	MAXIMUM
+	CHAR
+	STX	RESULT+1
+	ENTA	,2
+	CHAR
+	STX	RESULT+3
+	OUT	RESULT(19)
+	HLT
+	END	MAIN

sys/src/games/mix/examples/primes.m

@@ -0,0 +1,49 @@
+L	EQU	500
+PRINTER	EQU	18
+PRIME	EQU	-1
+BUF0	EQU	2000
+BUF1	EQU	BUF0+25
+	ORIG	3000
+START	IOC	0(PRINTER)
+	LD1	=1-L=
+	LD2	=3=
+2H	INC1	1
+	ST2	PRIME+L,1
+	J1Z	2F
+4H	INC2	2
+	ENT3	2
+6H	ENTA	0
+	ENTX	0,2
+	DIV	PRIME,3
+	JXZ	4B
+	CMPA	PRIME,3
+	INC3	1
+	JG	6B
+	JMP	2B
+2H	OUT	TITLE(PRINTER)
+	ENT4	BUF1+10
+	ENT5	-50
+2H	INC5	L+1
+4H	LDA	PRIME,5
+	CHAR
+	STX	0,4(1:4)
+	DEC4	1
+	DEC5	50
+	J5P	4B
+	OUT	0,4(PRINTER)
+	LD4	24,4
+	J5N	2B
+	HLT
+ORIG	PRIME+1
+	CON	2
+	ORIG	BUF0-5
+TITLE	ALF	"FIRST"
+	ALF	" FIVE"
+	ALF	" HUND"
+	ALF	"RED P"
+	ALF	"RIMES"
+	ORIG	BUF0+24
+	CON	BUF1+10
+	ORIG	BUF1+24
+	CON	BUF0+10
+	END	START

sys/src/games/mix/repl.c

@@ -211,7 +211,7 @@ repl(int go)
 
 	Binit(&bin, 0, OREAD);
 
-	if(go) {
+	if(go && vmstart != -1) {
 		once = 0;
 		goto Go;
 	}
@@ -277,6 +277,8 @@ repl(int go)
 				vmstart = mixvm(vmstart, once);
 			else
 				break;
+			if(go)
+				exits(nil);
 			if(vmstart == -1)
 				print("halted\n");
 			else