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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><!-- Macro Operators --><HTML><HEAD><TITLE>Macro Operators</TITLE></HEAD><BODY BACKGROUND="spiral.gif" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#990099" ALINK="#FF0000"><TABLE WIDTH="98%"><TR><TD WIDTH=60 VALIGN=BOTTOM NOWRAP><IMG SRC="transp.gif" ALT="" WIDTH=60 HEIGHT=20></TD><TD><!-- Ab hier Seitentext: --><BIG><BR><P><STRONG><U>III.11.5 Macro Operators</U></STRONG></P><P>There are some special control characters, which are very useful for macrodefinition, call and expansion:</P><P><TABLE BORDER CELLPADDING=8><TR><TD ALIGN=CENTER NOWRAP><BIG>;;</BIG></TD> <TD NOWRAP><STRONG>Macro commentary</STRONG></TD> <TD>Normally, comments in body lines are also contained in the expanded lines. If a commentary begins with ';;' however, it is not stored during macro definition. Therefore, it doesn't consume memory space, and appears in the list file in the macro definition only, but not in the expanded lines.</TD></TR><TR><TD ALIGN=CENTER NOWRAP><BIG>!</BIG></TD> <TD NOWRAP><STRONG>Literal operator</STRONG></TD> <TD>If the escape character '!' precedes another printable character in a macro argument, the assembler is forced to treat that character literally. This means it will be passed to the macro, even if it is a control character, while the literal operator itself is removed.</TD></TR><TR><TD ALIGN=CENTER NOWRAP><BIG>< ></BIG></TD> <TD NOWRAP><STRONG>Literal brackets</STRONG></TD> <TD>If a macro argument is intended to contain separation or control characters, it must be enclosed in literal brackets < ... > to pass it to the macro as one argument string, while the outermost pair of brackets is removed. Literal brackets can be nested to any depth.</TD></TR><TR><TD ALIGN=CENTER NOWRAP><BIG>%</BIG></TD> <TD NOWRAP><STRONG>Evaluation</STRONG></TD> <TD>If a macro argument is preceded by the evaluation operator '%', it is interpreted as an expression, which will be evaluated before it is passed to the macro. The actual argument string will not be the expression itself, but a decimal ASCII representation of its value. The expression must be known on <NOBR>pass 1</NOBR>.</TD></TR><TR><TD ALIGN=CENTER NOWRAP><BIG>&</BIG></TD> <TD NOWRAP><STRONG>Substitution</STRONG></TD> <TD>The '&' character separates parameter names (local symbols) from surrounding text. Outside quoted strings and commentary it serves only as a general separation character. This applies always when a local symbol directly precedes or follows another alphanumeric string. Inside quoted strings and commentary, a local symbol must be preceded by '&' if it is to be substituted there.<BR> During every macro expansion, the assembler removes exactly one '&' from every sequence of '&' characters. This allows for example, to define a nested macro inside a macro body, which also uses the substitution operator '&': one writes simply '&&'!</TD></TR></TABLE></P><P><BR><STRONG>Example 1:</STRONG><BLOCKQUOTE>The commentary should only be visible in the definitionof the macro LICENSE:<PRE> LICENSE MACRO DB 'Copyright' ;;legal stuff ENDM</PRE>When called, the expanded macro body is lookinglike this in the list file:<PRE> DB 'Copyright'</PRE></BLOCKQUOTE></P><P><BR><STRONG>Example 2:</STRONG><BLOCKQUOTE><PRE> SPECIAL !;</PRE>passes a semicolon to the macro SPECIAL as a literalargument. This could also be done with<PRE> SPECIAL <;></PRE></BLOCKQUOTE></P><P><BR><STRONG>Example 3:</STRONG><BLOCKQUOTE>The macro CONST defines a 16-bit constant in ROM:<PRE> CONST MACRO NUMB DW NUMB ENDM</PRE>If it is called as shown below,<PRE> CONST 0815H+4711-42</PRE>the parameter NUMB would be substituted as follows:<PRE> DW 0815H+4711-42</PRE>If the same macro argument is preceded by a '%' however,<PRE> CONST %0815H+4711-42</PRE>the substitution will result in:<PRE> DW 6738</PRE></BLOCKQUOTE></P><P><BR><STRONG>Example 4:</STRONG><BLOCKQUOTE>During substitution, both arguments of the macro CONCATshould form a seamless symbol name:<PRE> CONCAT MACRO NAM, NUM MOV R3,#0NAM&NUM: DJNZ R3,NAM&NUM ENDM</PRE>When CONCAT is called as follows,<PRE> CONCAT LABEL, 08</PRE>the parameters NAM and NUM are substituted during macroexpansion as shown below:<PRE> MOV R3,#0LABEL08: DJNZ R3,LABEL08</PRE></BLOCKQUOTE></P></BIG><!-- Seitentext Ende --><P><BR><BR><CENTER><TABLE WIDTH="70%"><TR><TH><A HREF="contents.htm"><IMG SRC="home.gif" ALT="[contents]" BORDER=0 WIDTH=32 HEIGHT=32></A></TH> <TH><A HREF="macros.htm"><IMG SRC="up.gif" ALT="[up]" BORDER=0 WIDTH=32 HEIGHT=32></A></TH> <TH><A HREF="local.htm"><IMG SRC="back.gif" ALT="[back]" BORDER=0 WIDTH=32 HEIGHT=32></A></TH> <TH><A HREF="exitm.htm"><IMG SRC="next.gif" ALT="[next]" BORDER=0 WIDTH=32 HEIGHT=32></A></TH></TR></TABLE></CENTER></P></TD></TR></TABLE></BODY></HTML>⌨️ 快捷键说明
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