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<html><head><title>VM Spec </title></head><body BGCOLOR=#eeeeff text=#000000 LINK=#0000ff VLINK=#000077 ALINK=#ff0000> <a href="VMSpecTOC.doc.html">Contents</a> | <a href="Instructions2.doc69.html">Prev</a> | <a href="Instructions2.doc71.html">Next</a> | <a href="Mnemonics.doc.html">Index</a><hr><br> <a name="fsub"></a><h2>fsub</h2><a name="fsub.Operation"></a><b>Operation</b><br><a name="68208"></a>Subtract <code>float</code><p><Table Border="3"><tr><td><a name="68207"></a> <i>fsub</i><td><a name="87568"></a> </Table><Table><tr><td></Table><p><a name="fsub.Forms"></a><b>Forms</b><br><a name="68209"></a><i>fsub</i> = 102 (0x66)<p><a name="fsub.Stack"></a><b>Stack</b><br><a name="68210"></a>..., <i>value1</i><em>, </em><i>value2</i> <img src="chars/arrwdbrt.gif"> ..., <i>result</i><p><a name="fsub.Description"></a><b>Description</b><br><a name="68211"></a>Both <i>value1</i> and <i>value2</i> must be of type <code>float</code>. The values are popped from the operand stack. The <code>float</code> <i>result</i> is <i>value1</i> - <i>value2</i>. The <i>result</i> is pushed onto the operand stack.<p><a name="68212"></a>For <code>float</code> subtraction, it is always the case that <code>a-b</code> produces the same result as <code>a+(-b)</code>. However, for the <i>fsub</i> instruction, subtraction from zero is not the same as negation, because if <code>x</code> is <code>+0.0</code>, then <code>0.0-x</code> equals <code>+0.0</code>, but <code>-x</code> equals <code>-0.0</code>. <p><a name="68213"></a>The Java Virtual Machine requires support of gradual underflow as defined by IEEE 754. Despite the fact that overflow, underflow, or loss of precision may occur, execution of an <i>fsub</i> instruction never throws a runtime exception.<p><hr><!-- This inserts footnotes--><p><a href="VMSpecTOC.doc.html">Contents</a> | <a href="Instructions2.doc69.html">Prev</a> | <a href="Instructions2.doc71.html">Next</a> | <a href="Mnemonics.doc.html">Index</a><p><font size=-1>Java Virtual Machine Specification (HTML generated by dkramer on February 25, 1997)<br><i><a href="Copyright.doc.html">Copyright © 1996 Sun Microsystems, Inc.</a>All rights reserved</i><br>Please send any comments or corrections to <a href="mailto:doug.kramer@sun.com">doug.kramer@sun.com</a></font></body></html>⌨️ 快捷键说明
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