File r37/lisp/csl/html/r37_0054.html artifact 7c917d7f0a part of check-in 2f3b3fd537

<A NAME=OR>

<TITLE>OR</TITLE></A>
<b><a href=r37_idx.html>INDEX</a></b><p><p>



<B>OR</B> _ _ _  _ _ _  _ _ _  _ _ _ <B>operator</B><P>
<P>
 
The <em>or</em> binary logical operator returns true if either one or 
both of its arguments is true. 
 <P> <H3> 
syntax: </H3>
<P>
<P>
&lt;logical expression&gt; <em>or</em> &lt;logical expression&gt; 
<P>
<P>
<P>
&lt;logical expression&gt; must evaluate to true or nil. 
<P>
<P>
 <P> <H3> 
examples: </H3>
<P><PRE><TT>
a := 10; 

  A := 10 


if a&lt;0 or a&gt;140 then write &quot;not a valid human age&quot; else
   write &quot;age = &quot;,a;
 



  age = 10 


a := 200; 

  A := 200 


if a &lt; 0 or a &gt; 140 then write &quot;not a valid human age&quot;;
			 


  not a valid human age

</TT></PRE><P>The <em>or</em> operator is left associative: <em>x or y or z</em>
 is equivalent to 
<em>(x or y)</em> <em>or z</em>. 
<P>
<P>
Logical operators can only be used in conditional expressions, such as 
<P>
<P>

<A HREF=r37_0052.html>if</A>...<em>then</em>...<em>else</em> 
and 
<A HREF=r37_0228.html>while</A>...<em>do</em>. 
<em>or</em> evaluates its arguments in order and quits, returning true, 
on finding the first true statement. 
<P>
<P>
<P>