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<center><b><big><big>Printing AD Values During Forward Mode</big></big></b></center>
<br/>
<b><big><a name="Syntax" id="Syntax">Syntax</a></big></b>

<br/>

<code><i><font color="black"><span style='white-space: nowrap'>f</span></font></i><font color="blue"><span style='white-space: nowrap'>.Forward(0,&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>)<br/>
</span></font></code>

<code><font color="blue"><span style='white-space: nowrap'>PrintFor(</span></font><i><font color="black"><span style='white-space: nowrap'>before</span></font></i><font color="blue"><span style='white-space: nowrap'>,&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>var</span></font></i><font color="blue"><span style='white-space: nowrap'>)<br/>
</span></font></code>

<code><font color="blue"><span style='white-space: nowrap'>PrintFor(</span></font><i><font color="black"><span style='white-space: nowrap'>pos</span></font></i><font color="blue"><span style='white-space: nowrap'>,&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>before</span></font></i><font color="blue"><span style='white-space: nowrap'>,&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>var</span></font></i><font color="blue"><span style='white-space: nowrap'>,&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>after</span></font></i><font color="blue"><span style='white-space: nowrap'>)<br/>
</span></font></code>
<br/>
<b><big><a name="Purpose" id="Purpose">Purpose</a></big></b>
<br/>
The <a href="forward_zero.xml" target="_top"><span style='white-space: nowrap'>zero&#xA0;order&#xA0;forward</span></a>
 mode command

<code><font color="blue"><span style='white-space: nowrap'><br/>
&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>f</span></font></i><font color="blue"><span style='white-space: nowrap'>.Forward(0,&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>)<br/>
</span></font></code>
assigns the 
<a href="glossary.xml#Tape.Independent Variable" target="_top"><span style='white-space: nowrap'>independent&#xA0;variable</span></a>
 vector
equal to 
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
.
It then computes a value for all of the dependent variables in the 
<a href="glossary.xml#Operation.Sequence" target="_top"><span style='white-space: nowrap'>operation&#xA0;sequence</span></a>
 corresponding
to 
<code><i><font color="black"><span style='white-space: nowrap'>f</span></font></i></code>
.
Putting a <code><font color="blue">PrintFor</font></code> in the operation sequence will
cause the value of 
<code><i><font color="black"><span style='white-space: nowrap'>var</span></font></i></code>
, corresponding to 
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
,
to be printed during zero order forward operations.

<br/>
<br/>
<b><big><a name="f.Forward(0, x)" id="f.Forward(0, x)">f.Forward(0, x)</a></big></b>
<br/>
The objects 
<code><i><font color="black"><span style='white-space: nowrap'>f</span></font></i></code>
, 
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
, and the purpose
for this operation, are documented in <a href="forward.xml" target="_top"><span style='white-space: nowrap'>Forward</span></a>
.

<br/>
<br/>
<b><big><a name="pos" id="pos">pos</a></big></b>
<br/>
If present, the argument 
<code><i><font color="black"><span style='white-space: nowrap'>pos</span></font></i></code>
 has one of the following prototypes

<code><font color="blue"><span style='white-space: nowrap'><br/>
&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;const&#xA0;AD&lt;</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>&gt;&amp;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>pos</span></font></i><font color="blue"><span style='white-space: nowrap'><br/>
&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;const&#xA0;VecAD&lt;</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>&gt;::reference&amp;&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>pos</span></font></i><font color="blue"><span style='white-space: nowrap'><br/>
</span></font></code>
In this case
the text and 
<code><i><font color="black"><span style='white-space: nowrap'>var</span></font></i></code>
 will be printed if and only if

<code><i><font color="black"><span style='white-space: nowrap'>pos</span></font></i></code>
 is not greater than zero and a finite number.

<br/>
<br/>
<b><big><a name="before" id="before">before</a></big></b>
<br/>
The argument 
<code><i><font color="black"><span style='white-space: nowrap'>before</span></font></i></code>
 has prototype

<code><font color="blue"><span style='white-space: nowrap'><br/>
&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;const&#xA0;char*&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>before</span></font></i><font color="blue"><span style='white-space: nowrap'><br/>
</span></font></code>
This text is written to <code><font color="blue">std::cout</font></code> before 
<code><i><font color="black"><span style='white-space: nowrap'>var</span></font></i></code>
. 

<br/>
<br/>
<b><big><a name="var" id="var">var</a></big></b>
<br/>
The argument 
<code><i><font color="black"><span style='white-space: nowrap'>var</span></font></i></code>
 has one of the following prototypes

<code><font color="blue"><span style='white-space: nowrap'><br/>
&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;const&#xA0;AD&lt;</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>&gt;&amp;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>var</span></font></i><font color="blue"><span style='white-space: nowrap'><br/>
&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;const&#xA0;VecAD&lt;</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>&gt;::reference&amp;&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>var</span></font></i><font color="blue"><span style='white-space: nowrap'><br/>
</span></font></code>
The value of 
<code><i><font color="black"><span style='white-space: nowrap'>var</span></font></i></code>
, that corresponds to 
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
,
is written to <code><font color="blue">std::cout</font></code> during the execution of 

<code><font color="blue"><span style='white-space: nowrap'><br/>
&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>f</span></font></i><font color="blue"><span style='white-space: nowrap'>.Forward(0,&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>)<br/>
</span></font></code>
Note that 
<code><i><font color="black"><span style='white-space: nowrap'>var</span></font></i></code>
 may be a
<a href="glossary.xml#Variable" target="_top"><span style='white-space: nowrap'>variable</span></a>
 or 
<a href="glossary.xml#Parameter" target="_top"><span style='white-space: nowrap'>parameter</span></a>
.
(A parameters value does not depend on the value of 
the independent variable vector 
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
.)

<br/>
<br/>
<b><big><a name="after" id="after">after</a></big></b>
<br/>
The argument 
<code><i><font color="black"><span style='white-space: nowrap'>after</span></font></i></code>
 has prototype

<code><font color="blue"><span style='white-space: nowrap'><br/>
&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;const&#xA0;char*&#xA0;</span></font><i><font color="black"><span style='white-space: nowrap'>after</span></font></i><font color="blue"><span style='white-space: nowrap'><br/>
</span></font></code>
This text is written to <code><font color="blue">std::cout</font></code> after 
<code><i><font color="black"><span style='white-space: nowrap'>var</span></font></i></code>
. 
	
<br/>
<br/>
<b><big><a name="Discussion" id="Discussion">Discussion</a></big></b>
<br/>
This is helpful for understanding why tape evaluations
have trouble.
For example, if one of the operations in 
<code><i><font color="black"><span style='white-space: nowrap'>f</span></font></i></code>
 is

<code><font color="blue"><span style='white-space: nowrap'>log(</span></font><i><font color="black"><span style='white-space: nowrap'>var</span></font></i><font color="blue"><span style='white-space: nowrap'>)</span></font></code>
 and 
<code><i><font color="black"><span style='white-space: nowrap'>var</span></font></i><font color="blue"><span style='white-space: nowrap'>&#xA0;&lt;=&#xA0;0</span></font></code>
,
the corresponding result will be <a href="nan.xml" target="_top"><span style='white-space: nowrap'>nan</span></a>
.

<br/>
<br/>
<b><big><a name="Alternative" id="Alternative">Alternative</a></big></b>
<br/>
The <a href="ad_output.xml" target="_top"><span style='white-space: nowrap'>ad_output</span></a>
 section describes the normal 
printing of values; i.e., printing when the corresponding
code is executed.

<br/>
<br/>
<b><big><a name="Example" id="Example">Example</a></big></b>

<br/>
The program
<a href="print_for_cout.cpp.xml" target="_top"><span style='white-space: nowrap'>print_for_cout.cpp</span></a>

is an example and test that prints to standard output.
The output of this program
states the conditions for passing and failing the test.
The function
<a href="print_for_string.cpp.xml" target="_top"><span style='white-space: nowrap'>print_for_string.cpp</span></a>

is an example and test that prints to an standard string stream.
This function automatically check for correct output.


<hr/>Input File: cppad/local/print_for.hpp

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