More MACRO-10 parsing improvements

apps/pdp10/tests/MACTEST.MAC.txt

@@ -1,4 +1,23 @@
-	TITLE 	STORE TEXT CHARACTER BY CHARACTER
+; From the MACR0-10 ASSEMBLER PROGRAMMER'S REFERENCE MANUAL (June 1972):
+;
+;	Example 4 (Figure 7-4) shows nested macros which use IRPC.  The desired operation
+;	is to take an ASCII text string and store the characters four per word, left-justified,
+;	with the character count stored in the first nine bits of the first word.
+;
+;	The TEXT macro counts the string characters and invokes the CODE macro to store the
+;	characters four per word.  The CODE macro invokes a SHIFT macro which left-justifies the
+;	last word if it is not already left-justified.  The first part of the example shows the
+;	normal listing, then SALL is set to show what code the macros are generating.
+;
+; The original listing encodes the following two lines as follows:
+;
+;	IFN ZZ,<DEFINE SHIFT		;;REMAINDER LEFT
+;	 IFE ZZ&777B8,>			;;IF NOT LEFT JUSTIFIED
+;
+; The April 1978 MACRO-10 manual says that a macro body "must be enclosed in angle brackets",
+; so I'm not sure how the above lines make sense.
+;
+	TITLE	STORE TEXT CHARACTER BY CHARACTER
 	SUBTTL	%1 5-APR-72
 
 	DEFINE TEXT (C)<
@@ -13,10 +32,10 @@
 	IFN ZZ&777B8,<
 		EXP ZZ			;;WORD FULL
 		ZZ==0>			;;START AGAIN WITH 0
-	ZZ=ZZ+9+"C">			;;END OF IRPC
+	ZZ==ZZ_9+"C">			;;END OF IRPC
 	IFN ZZ,<DEFINE SHIFT<		;;REMAINDER LEFT
 	 IFE ZZ&777B8,<			;;IF NOT LEFT JUSTIFIED
-	  ZZ=ZZ+9			;;MOVE LEFT 9 BITS
+	  ZZ==ZZ_9			;;MOVE LEFT 9 BITS
 	  SHIFT>			;;RECURSE
 	 >				;;END OF DEFINE
 	SHIFT				;;START MOVING LEFT