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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-AC99E9ED-2C02-561A-ABA4-DCDD415E8653" xml:lang="en"><title>Math

    13 functions</title><shortdesc>Describes the maths functions used by application programs.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <section id="GUID-965ABD80-2C30-43D1-8F40-7BF573301630"><title>Calling syntax</title> <p>Math functions are designed for

    15 use by application programs which must be able firstly to do the desired calculation

    16 and secondly to handle error conditions arising from the calculations. Thus,

    17 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

    18 double a; // result

    19 a=sin(x); // typical use</codeblock> <p>are not implemented by the Symbian

    20 software platform. Rather, all functions return error information explicitly.</p> <p>All

    21 functions are provided as static member functions of the <codeph>Math</codeph> class.

    22 This is a convenient packaging mechanism. A typical math function is thus

    23 declared like this:</p> <codeblock id="GUID-C363CF23-CE56-59FA-A4EB-2DA2AD886C0D" xml:space="preserve">class Math

    24     {

    25 public:

    26     // ...

    27     static TInt Sin(TReal &aTrg,const TReal &aSrc);

    28     // ...

    29     };</codeblock> <p>and used like this:</p> <codeblock id="GUID-EA13F019-D473-5757-B036-8461BD3B0143" xml:space="preserve">TReal x=1; // argument

    30 TReal a; // result

    31 TInt matherror; // error indication

    32 matherror=Math::ASin(a,x); // get result and error

    33 User::LeaveIfError(matherror); // handle error</codeblock> <p>This syntax

    34 is unusual for those used to the ANSI library. However, the ANSI library functions

    35 are designed for speed, and for users whose programs control the valid range

    36 of the arguments, and can thus reasonably ensure that they are within range.

    37 The <codeph>Math</codeph> class, however, provides direct support to expression

    38 interpreters acting on numbers entered by users. In this context, error checking

    39 is a vital part of the process.</p> <p>In most cases, the same variable may

    40 be used for both argument and result, i.e., <codeph>Math::Sin(x,x)</codeph> will

    41 work as expected, because the function has finished with the argument by the

    42 time the result is written to.</p> </section>

    43 <section id="GUID-8633E2E3-316D-40AE-9F88-77E6CF7FA041"><title>Precision</title> <p>The <codeph>TReal</codeph> type is equated

    44 to <codeph>double</codeph>. With an IEEE754 floating-point implementation,

    45 this gives a range from about 2.225074 × 10<sup>–</sup> <sup>308</sup> to

    46 about 1.797693 × 10<sup>+308</sup>, and an accuracy of 15 decimal places.</p> </section>

    47 <section id="GUID-2D26DDD3-FE18-4D0A-AC10-F445708750BB"><title>Error indications</title> <p>All functions return a standard

    48 error code. </p> </section>

    49 </conbody></concept>