----common functions and constants of iOS development

<span id="Label3"></p><p><p>Introduce the functions commonly used in objective-c, constant variables</p></p>Arithmetic functions <table border="1"> <caption> "arithmetic function" </caption> <colgroup width="200"></colgroup> <colgroup width="340"></colgroup> <thead> <tr> <th>Name of function</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td>int Rand ()</td> <td>Random number Generation.<br>Cases<br>Srand (time (nil)); Initial random number initialization<br>int val = rand () P; Random number between 0~49</td> </tr> <tr> <td>int ABS (int A)</td> <td>Absolute value of an integer<br>(example) int val = ABS (-8);<br>→8<br>* Use fabs when floating-point numbers.</td> </tr> <tr> <td>Double Fabs (double A)</td> <td>Absolute value of floating-point numbers<br>(example) double val = fabs (-12.345);<br>→12.345<br>※the whole number is used Abs.</td> </tr> <tr> <td>Double Floor (double A)</td> <td>Returns the integer portion of a floating-point number (discarding a decimal point)<br>(example) double val = floor (12.345);<br>→12.000</td> </tr> <tr> <td>Double Ceil (double a);</td> <td>Returns the integer portion of a floating-point number (discards the decimal point and enters 1 digits)<br>(example) double val = ceil (12.345);<br>→13.000</td> </tr> <tr> <td>Double POW (double a, double b)</td> <td>A's b-square<br>(example) double val = pow (2, 3);<br>→8</td> </tr> <tr> <td>Double sqrt (double A)</td> <td>Square root of a<br>(example) double val = sqrt (2);<br>→1.41421356</td> </tr> </tbody> </table>Trigonometric function <table border="1"> <caption> Trigonometric functions </caption> <colgroup width="200"></colgroup> <colgroup width="340"></colgroup> <thead> <tr> <th>Name of function</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td>Double cos (double a)</td> <td>cosine function (a: Radians)</td> </tr> <tr> <td>Double Sin (double a)</td> <td>sine function (a: Radians)</td> </tr> <tr> <td>Double Tan (double A)</td> <td>Tangent function (a: Radians)</td> </tr> <tr> <td>Double ASIN (double A)</td> <td>Inverse Chord value (a: Radians)</td> </tr> <tr> <td>Double ACOs (double A)</td> <td>Inverse cosine function (a: Radians)</td> </tr> <tr> <td>Double Atan (double A)</td> <td>Inverse tangent function</td> </tr> <tr> <td>Double atan2 (double a, double B)</td> <td>Returns the inverse tangent value of the given a and B coordinate values</td> </tr> </tbody> </table>exponential function <table border="1"> <caption> "exponential function" </caption> <colgroup width="200"></colgroup> <colgroup width="340"></colgroup> <thead> <tr> <th>Name of function</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td>Double Log (double A)</td> <td>The value of the pairs based on the base E</td> </tr> <tr> <td>Double log10 (double A)</td> <td>Log function Log</td> </tr> </tbody> </table>Constant<p><p></p></p> <table border="1"> <caption> Constant </caption> <colgroup width="200"></colgroup> <colgroup width="340"></colgroup> <thead> <tr> <th>Constant Number name</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td>M_pi</td> <td>Pi (=π)</td> </tr> <tr> <td>M_pi_2</td> <td>1/2 of Pi (=π/2)</td> </tr> <tr> <td>M_pi_4</td> <td>1/4 of Pi (=π/4)</td> </tr> <tr> <td>M_1_pi</td> <td>=1/π</td> </tr> <tr> <td>M_2_pi</td> <td>=2/π</td> </tr> <tr> <td>M_e</td> <td>=e</td> </tr> <tr> <td>m_log2e</td> <td>Log_2 (e)</td> </tr> <tr> <td>m_log10e</td> <td>Log_10 (e)</td> </tr> </tbody> </table><p><p>Original Link:----common functions and constants of iOS development</p></p><p><p>----common functions and constants of iOS development</p></p></span>