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 <h3 class="section">1.40 <code>matherr</code>&mdash;modifiable math error handler</h3>

 <p><a name="index-matherr-116"></a><strong>Synopsis</strong>
 <pre class="example">     #include &lt;math.h&gt;
      int matherr(struct exception *<var>e</var>);

 </pre>
    <p><strong>Description</strong><br>
 <code>matherr</code> is called whenever a math library function generates an error.
 You can replace <code>matherr</code> by your own subroutine to customize
 error treatment.  The customized <code>matherr</code> must return 0 if
 it fails to resolve the error, and non-zero if the error is resolved.

    <p>When <code>matherr</code> returns a nonzero value, no error message is printed
 and the value of <code>errno</code> is not modified.  You can accomplish either
 or both of these things in your own <code>matherr</code> using the information
 passed in the structure <code>*</code><var>e</var>.

    <p>This is the <code>exception</code> structure (defined in `<code>math.h</code>'):
 <pre class="smallexample">     	struct exception {
      	        int type;
      	        char *name;
      	        double arg1, arg2, retval;
      		int err;
      	};
 </pre>
    <p>The members of the exception structure have the following meanings:
      <dl>
 <dt><code>type</code><dd>The type of mathematical error that occured; macros encoding error
 types are also defined in `<code>math.h</code>'.

      <br><dt><code>name</code><dd>a pointer to a null-terminated string holding the
 name of the math library function where the error occurred.

      <br><dt><code>arg1, arg2</code><dd>The arguments which caused the error.

      <br><dt><code>retval</code><dd>The error return value (what the calling function will return).

      <br><dt><code>err</code><dd>If set to be non-zero, this is the new value assigned to <code>errno</code>.
 </dl>

    <p>The error types defined in `<code>math.h</code>' represent possible mathematical
 errors as follows:

      <dl>
 <dt><code>DOMAIN</code><dd>An argument was not in the domain of the function; e.g. <code>log(-1.0)</code>.

      <br><dt><code>SING</code><dd>The requested calculation would result in a singularity; e.g. <code>pow(0.0,-2.0)</code>

      <br><dt><code>OVERFLOW</code><dd>A calculation would produce a result too large to represent; e.g.
 <code>exp(1000.0)</code>.

      <br><dt><code>UNDERFLOW</code><dd>A calculation would produce a result too small to represent; e.g.
 <code>exp(-1000.0)</code>.

      <br><dt><code>TLOSS</code><dd>Total loss of precision.  The result would have no significant digits;
 e.g. <code>sin(10e70)</code>.

      <br><dt><code>PLOSS</code><dd>Partial loss of precision.
 </dl>

    <p><br>
 <strong>Returns</strong><br>
 The library definition for <code>matherr</code> returns <code>0</code> in all cases.

    <p>You can change the calling function's result from a customized <code>matherr</code>
 by modifying <code>e-&gt;retval</code>, which propagates backs to the caller.

    <p>If <code>matherr</code> returns <code>0</code> (indicating that it was not able to resolve
 the error) the caller sets <code>errno</code> to an appropriate value, and prints
 an error message.

    <p><br>
 <strong>Portability</strong><br>
 <code>matherr</code> is not ANSI C.

    <p><br>

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	</div>

	<h3 class="section">1.40 <code>matherr</code>—modifiable math error handler</h3>

	<p><a name="index-matherr-116"></a><strong>Synopsis</strong>
	<pre class="example"> #include <math.h>
	int matherr(struct exception *<var>e</var>);

	</pre>
	<p><strong>Description</strong><br>
	<code>matherr</code> is called whenever a math library function generates an error.
	You can replace <code>matherr</code> by your own subroutine to customize
	error treatment. The customized <code>matherr</code> must return 0 if
	it fails to resolve the error, and non-zero if the error is resolved.

	<p>When <code>matherr</code> returns a nonzero value, no error message is printed
	and the value of <code>errno</code> is not modified. You can accomplish either
	or both of these things in your own <code>matherr</code> using the information
	passed in the structure <code>*</code><var>e</var>.

	<p>This is the <code>exception</code> structure (defined in `<code>math.h</code>'):
	<pre class="smallexample"> struct exception {
	int type;
	char *name;
	double arg1, arg2, retval;
	int err;
	};
	</pre>
	<p>The members of the exception structure have the following meanings:
	<dl>
	<dt><code>type</code><dd>The type of mathematical error that occured; macros encoding error
	types are also defined in `<code>math.h</code>'.

	<br><dt><code>name</code><dd>a pointer to a null-terminated string holding the
	name of the math library function where the error occurred.

	<br><dt><code>arg1, arg2</code><dd>The arguments which caused the error.

	<br><dt><code>retval</code><dd>The error return value (what the calling function will return).

	<br><dt><code>err</code><dd>If set to be non-zero, this is the new value assigned to <code>errno</code>.
	</dl>

	<p>The error types defined in `<code>math.h</code>' represent possible mathematical
	errors as follows:

	<dl>
	<dt><code>DOMAIN</code><dd>An argument was not in the domain of the function; e.g. <code>log(-1.0)</code>.

	<br><dt><code>SING</code><dd>The requested calculation would result in a singularity; e.g. <code>pow(0.0,-2.0)</code>

	<br><dt><code>OVERFLOW</code><dd>A calculation would produce a result too large to represent; e.g.
	<code>exp(1000.0)</code>.

	<br><dt><code>UNDERFLOW</code><dd>A calculation would produce a result too small to represent; e.g.
	<code>exp(-1000.0)</code>.

	<br><dt><code>TLOSS</code><dd>Total loss of precision. The result would have no significant digits;
	e.g. <code>sin(10e70)</code>.

	<br><dt><code>PLOSS</code><dd>Partial loss of precision.
	</dl>

	<p><br>
	<strong>Returns</strong><br>
	The library definition for <code>matherr</code> returns <code>0</code> in all cases.

	<p>You can change the calling function's result from a customized <code>matherr</code>
	by modifying <code>e->retval</code>, which propagates backs to the caller.

	<p>If <code>matherr</code> returns <code>0</code> (indicating that it was not able to resolve
	the error) the caller sets <code>errno</code> to an appropriate value, and prints
	an error message.

	<p><br>
	<strong>Portability</strong><br>
	<code>matherr</code> is not ANSI C.

	<p><br>

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