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<I><H2>Integer and Boolean expressions
</H2></I>
<HR>
<P>An expression can be composed of many things. Expressions are always evaluated using signed 32-bit math.
<P>The most basic expression is just a single number.
<H4><BR>Numeric Formats</H4>
<P>xAsm has a number of numeric formats.
<UL>
<LI>Hexadecimal: $0123456789ABCDEF. Case-insensitive
<LI>Decimal: 0123456789
<LI>Octal: &01234567
<LI>Binary: %01
<LI>Fixedpoint (16.16): 01234.56789
<LI>Character constant: "ABYZ"
<LI>Gameboy graphics: `0123
</UL>
<P>The last one, Gameboy graphics, is quite interesting and useful. The values are actually pixel values and it converts
the "chunky" data to "planar" data as used in the Gameboy.<BR>
<BR>
<TABLE BORDER=0 BGCOLOR="Black" CELLPADDING=8 WIDTH="50%">
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<TD><FONT COLOR="#00FF00">
<PRE>DW `01012323</PRE>
</FONT></TD>
</TR>
</TABLE>
Admittedly an expression with just a single number is quite boring. To spice things up a bit there's a few operators you can use to perform calculations between numbers.
<H4><BR>
Operators</H4>
<P>A great number of operators you can use in expressions are available (listed in order of precedence):
<TABLE BORDER=1>
<CAPTION><I>Operators</I></CAPTION>
<TR>
<TD><B><I>Operator</I></B></TD>
<TD><B><I>Meaning</I></B></TD>
</TR>
<TR>
<TD>( )</TD>
<TD>Precedence override</TD>
</TR>
<TR>
<TD>FUNC()</TD>
<TD>Functioncall</TD>
</TR>
<TR>
<TD>~ + -</TD>
<TD>Unary not/plus/minus</TD>
</TR>
<TR>
<TD>* / %</TD>
<TD>Multiply/divide/modulo</TD>
</TR>
<TR>
<TD><< >></TD>
<TD>Shift left/right</TD>
</TR>
<TR>
<TD>& | ^</TD>
<TD>Binary and/or/xor</TD>
</TR>
<TR>
<TD>+ -</TD>
<TD>Add/subtract</TD>
</TR>
<TR>
<TD>!= == <= >= < ></TD>
<TD>Boolean comparison</TD>
</TR>
<TR>
<TD>&& ||</TD>
<TD>Boolean and/or</TD>
</TR>
<TR>
<TD>!</TD>
<TD>Unary Boolean not</TD>
</TR>
</TABLE>
<P>The result of the boolean operators is zero if when FALSE and non-zero when TRUE. Thus it is legal to use an integer as the condition for <A HREF="if.htm">IF</A> blocks. You can use symbols instead of numbers in your expression if you wish.
<P>An expression is said to be constant when it doesn't change its value during linking. This basically means that you can't use labels in those expressions. The instructions in the macro-language all require expressions that are constant<BR>
<H3>See also:</H3>
<UL>
<LI><A HREF="symbols.htm">Symbols</A>
<LI><A HREF="expr_fix.htm">Fixed-point expressions and functions</A>
<LI><A HREF="expr_str.htm">String expressions, functions and formatting</A>
<LI><A HREF="miscfunc.htm">Other functions</A>
</UL>
<BR><HR>
<FONT SIZE="-1"><I><P ALIGN=RIGHT>Last updated 21 June 1997 by <A HREF="mailto:[email protected]">Carsten Sorensen</A></P></I></FONT>