Documented the .SET operator that has been available for about 6 years now :-)

git-svn-id: svn://svn.cc65.org/cc65/trunk@5309 b7a2c559-68d2-44c3-8de9-860c34a00d81

doc/ca65.sgml

@@ -696,6 +696,39 @@ The right side can of course be an expression:
 </verb></tscreen>
 
 
+<label id=".SET">
+<sect1>Numeric variables<p>
+
+Within macros and other control structures (<tt><ref id=".REPEAT"
+name=".REPEAT"></tt>, ...) it is sometimes useful to have some sort of
+variable. This can be achieved by the <tt>.SET</tt> operator. It creates a
+symbol that may get assigned a different value later:
+
+<tscreen><verb>
+        four .set 4
+        lda     #four           ; Loads 4 into A
+        four .set 3
+        lda     #four           ; Loads 3 into A
+</verb></tscreen>
+
+Since the value of the symbol can change later, it must be possible to
+evaluate it when used (no delayed evaluation as with normal symbols). So the
+expression used as the value must be constant.
+
+Following is an example for a macro that generates a different label each time
+it is used. It uses the <tt><ref id=".SPRINTF" name=".SPRINTF"></tt> function
+and a numeric variable named <tt>lcount</tt>.
+
+<tscreen><verb>
+        .lcount .set 0          ; Initialize the counter
+
+        .macro  genlab
+                .ident (.sprintf ("L%04X", lcount)):
+                lcount .set lcount + 1
+        .endmacro
+</verb></tscreen>
+
+
 <sect1>Standard labels<p>
 
 A label is defined by writing the name of the label at the start of the line