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<TITLE>LambdaMOO Programmer's Manual - Precedence</TITLE>
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<H3><A NAME="SEC27" HREF="ProgrammersManual_toc.html#TOC27">Parentheses and Operator Precedence</A></H3>
<P>
As shown in a few examples above, MOO allows you to use parentheses to make it
clear how you intend for complex expressions to be grouped. For example, the
expression
</P>
<PRE>
3 * (4 + 5)
</PRE>
<P>
performs the addition of 4 and 5 before multiplying the result by 3.
</P>
<P>
If you leave out the parentheses, MOO will figure out how to group the
expression according to certain rules. The first of these is that some
operators have higher <STRONG>precedence</STRONG> than others; operators with higher
precedence will more tightly bind to their operands than those with lower
precedence. For example, multiplication has higher precedence than addition;
thus, if the parentheses had been left out of the expression in the previous
paragraph, MOO would have grouped it as follows:
</P>
<PRE>
(3 * 4) + 5
</PRE>
<P>
The table below gives the relative precedence of all of the MOO
operators; operators on higher lines in the table have higher precedence
and those on the same line have identical precedence:
</P>
<PRE>
! - (without a left operand)
^
* / %
+ -
== != < <= > >= in
&& ||
... ? ... | ... (the conditional expression)
=
</PRE>
<P>
Thus, the horrendous expression
</P>
<PRE>
x = a < b && c > d + e * f ? w in y | - q - r
</PRE>
<P>
would be grouped as follows:
</P>
<PRE>
x = (((a < b) && (c > (d + (e * f)))) ? (w in y) | ((- q) - r))
</PRE>
<P>
It is best to keep expressions simpler than this and to use parentheses
liberally to make your meaning clear to other humans.
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