ref: bc6b2fe005d791e2d0d087aaeb9ba8fbb1065894
dir: /doc/asm/expr_int.htm/
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> <HTML> <HEAD> <TITLE>xAsm Integer/Boolean expressions</TITLE> </HEAD> <BODY BGCOLOR="#692764" TEXT="#F5A0D8" LINK="#8AAEE6" VLINK="#2B9DA4" ALINK="#95F0DA"> <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%"> <TR> <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>