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| author | Tobias Klauser <tklauser@distanz.ch> | 2008-01-27 11:37:44 +0100 |
|---|---|---|
| committer | Tobias Klauser <tklauser@xenon.tklauser.home> | 2008-01-27 11:37:44 +0100 |
| commit | 7e0f021a9aec35fd8e6725e87e3313b101d26f5e (patch) | |
| tree | b1cacc4b24393f517aeb4610e9e1021f954307a8 /reference/C/SYNTAX/logical.html | |
Initial import (2.0.2-6)2.0.2-6
Diffstat (limited to 'reference/C/SYNTAX/logical.html')
| -rw-r--r-- | reference/C/SYNTAX/logical.html | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/reference/C/SYNTAX/logical.html b/reference/C/SYNTAX/logical.html new file mode 100644 index 0000000..54cb246 --- /dev/null +++ b/reference/C/SYNTAX/logical.html @@ -0,0 +1,102 @@ +<title>Logical AND OR and NOT</title> +<head> +<script language="JavaScript"> +</script> +</head> +<body bgcolor="#ffffcc"> +<hr> +<center> +<h1>Logical AND OR and NOT</h1> +</center> +<hr> + +<ul> +<li><a href=#AND>Logical AND is &&</a> +<li><a href=#OR>Logical OR is ||</a> +<li><a href=#NOT>Logical NOT is !</a> +</ul> +<hr> +<a name=AND> +<h2>Logical AND</h2> +In simple terms, && is true (1) if both sides of the expression returns NOT 0. +<p> +For Example: +<pre> + /* These all return TRUE (1) */ + + if (4 && 5) return(); + + i=3; + j=2; + return( i && j); +</pre> +The expression is evaluated 'Left to Right' If any part of the expression +returns ZERO - The evaluation ends. +<p> +THIS CAN CAUSE SERIOUS PROBLEMS. +<p> +For example: +<pre> + k=0; + i=3; + j=2; + if ( i-i && j++) k=1 +</pre> +The left side <i>(i-i)</i> resolves to 0, so <i>j</i> is not incremented +and <i>k</i> is not changed. +<hr> +<a name=OR> +<h2>Logical OR</h2> +OR also evaluates 'Left to Right' and will stop when an expression +returns true. <p> +SO WATCH YOUR BACK.... +<p> +<pre> + k=0; + i=3; + j=2; + if ( i+i && j++) k=1 +</pre> +What are <i>j</i> and <i>k</i> going to be when this code is executed????? + +<hr> +<a name=NOT> +<h2>Logical NOT</h2> + +NOT reverses the logical state of its +<a href=../glossary.html#operand>operand</a>. If the operand is 0, 1 is +returned, else 0 is returned. + +<pre> + !4 /* Returns 0 */ + !-4 /* Returns 0 */ + !1 /* Returns 0 */ + !0 /* Returns 1 */ +</pre> + + +<p> + +<hr> +<p> +<center> +<table border=2 width="80%" bgcolor="ivory"> +<tr align=center> +<td width="25%"> +<a href="../cref.html"> Top</a> +</td><td width="25%"> +<a href="../master_index.html"> Master Index</a> +</td><td width="25%"> +<a href="keywords.html"> Keywords</a> +</td><td width="25%"> +<a href="../FUNCTIONS/funcref.htm"> Functions</a> +</td> +</tr> +</table> +</center> +<p> +<hr> +<address>Martin Leslie +</address><p> +</body> +</html> |