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  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="GUID-AC99E9ED-2C02-561A-ABA4-DCDD415E8653" xml:lang="en"><title>Math
functions</title><shortdesc>Describes the maths functions used by application programs.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<section id="GUID-965ABD80-2C30-43D1-8F40-7BF573301630"><title>Calling syntax</title> <p>Math functions are designed for
use by application programs which must be able firstly to do the desired calculation
and secondly to handle error conditions arising from the calculations. Thus,
the ANSI-style functions of the form</p> <codeblock id="GUID-C277F9D8-5FDD-5460-B059-DF02E36B4948" xml:space="preserve">double sin(double); // typical declaration</codeblock> <codeblock id="GUID-8A9C44FE-7EDF-59DB-AFE0-B48148CBE0C8" xml:space="preserve">double x=1; // argument
double a; // result
a=sin(x); // typical use</codeblock> <p>are not implemented by the Symbian
software platform. Rather, all functions return error information explicitly.</p> <p>All
functions are provided as static member functions of the <codeph>Math</codeph> class.
This is a convenient packaging mechanism. A typical math function is thus
declared like this:</p> <codeblock id="GUID-C363CF23-CE56-59FA-A4EB-2DA2AD886C0D" xml:space="preserve">class Math
    {
public:
    // ...
    static TInt Sin(TReal &amp;aTrg,const TReal &amp;aSrc);
    // ...
    };</codeblock> <p>and used like this:</p> <codeblock id="GUID-EA13F019-D473-5757-B036-8461BD3B0143" xml:space="preserve">TReal x=1; // argument
TReal a; // result
TInt matherror; // error indication
matherror=Math::ASin(a,x); // get result and error
User::LeaveIfError(matherror); // handle error</codeblock> <p>This syntax
is unusual for those used to the ANSI library. However, the ANSI library functions
are designed for speed, and for users whose programs control the valid range
of the arguments, and can thus reasonably ensure that they are within range.
The <codeph>Math</codeph> class, however, provides direct support to expression
interpreters acting on numbers entered by users. In this context, error checking
is a vital part of the process.</p> <p>In most cases, the same variable may
be used for both argument and result, i.e., <codeph>Math::Sin(x,x)</codeph> will
work as expected, because the function has finished with the argument by the
time the result is written to.</p> </section>
<section id="GUID-8633E2E3-316D-40AE-9F88-77E6CF7FA041"><title>Precision</title> <p>The <codeph>TReal</codeph> type is equated
to <codeph>double</codeph>. With an IEEE754 floating-point implementation,
this gives a range from about 2.225074 × 10<sup>–</sup> <sup>308</sup> to
about 1.797693 × 10<sup>+308</sup>, and an accuracy of 15 decimal places.</p> </section>
<section id="GUID-2D26DDD3-FE18-4D0A-AC10-F445708750BB"><title>Error indications</title> <p>All functions return a standard
error code. </p> </section>
</conbody></concept>