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Thursday, July 12, 2007

Working with Math Routines in C#

Environment:  C#, .NET

Basic math operators—such as plus, minus, and modulus—can get you only so far. It is only a matter of time before you find that you need more robust math routines. C# has access to a set of math routines within the base classes. These are available from within the System.Math namespace. Table 1 presents a number of the math methods available.

 

The Math class is sealed. A sealed class cannot be used for inheritance. Additionally, all the classes and data members are static, so you can't create an object of type Math. Instead, you use the members and methods with the class name.

Table 1: Math Routines in the Math Class

Method
Returns

Abs
Returns the absolute value of a number.

Ceiling
Returns a value that is the smallest whole number greater than or equal to a given number.

Exp
Returns E raised to a given power. This is the inverse of Log.

Floor
Returns a value that is the largest whole number that is less than or equal to the given number.

IEEERemainder
Returns the result of a division of two specified numbers. (This division operation conforms to the remainder operation stated within Section 5.1 of ANSI/IEEE Std. 754-1985; IEEE Standard for Binary Floating-Point Arithmetic; Institute of Electrical and Electronics Engineers, Inc; 1985.)

Log
Returns a value that is the logarithmic value of the given number.

Log10
Returns a value that is the base 10 logarithm of a given value.

Max
Returns the larger of two values.

Min
Returns the smaller of two values.

Pow
Returns the value of a given value raised to a given power.

Round
Returns a rounded value for a number. You can specify the precision of the rounded number. The number .5 would be rounded down.

Sign
Returns a value indicating the sign of a value. 1 is returned for a negative number, 0 is returned for zero, and 1 is returned for a positive number.

Sqrt
Returns the square root for a given value.

Acos
Returns the value of an angle whose cosine is equal to a given number.

Asin
Returns the value of an angle whose sine is equal to a given number.

Atan
Returns the value of an angle whose tangent is equal to a given number.

Atan2
Returns the value of an angle whose tangent is equal to the quotient of two given numbers.

Cos
Returns a value that is the cosine of a given angle.

Cosh
Returns a value that is the hyperbolic cosine for a given angle.

Sin
Returns the sine for a given angle.

Sinh
Returns the hyperbolic sine for a given angle.

Tan
Returns the tangent of a specified angle.

Tanh
Returns the hyperbolic tangent of a given angle.

The Math class also includes two constants: PI and E. PI returns the value of [PI] as 3.14159265358979323846. The E data member returns the value of the logarithmic base, 2.7182818284590452354.

Most of the math methods in Table 1 are easy to understand. Listing 1 presents a couple of the routines in use.

Listing 1: MathApp.cs — Using Some of the Math Routines

 1:  //  MathApp.cs - Using a Math routine
2: //-----------------------------------------------
3: using System;
4:
5: class MathApp
6: {
7: public static void Main()
8: {
9: int val2;
10: char disp;
11:
12: for (double ctr = 0.0; ctr <= 10; ctr += .2)
13: {
14: val2 = (int) Math.Round( ( 10 * Math.Sin(ctr))) ;
15: for( int ctr2 = -10; ctr2 <= 10; ctr2++ )
16: {
17: if (ctr2 == val2)
18: disp = 'X';
19: else
20: disp = ' ';
21:
22: Console.Write("{0}", disp);
23: }
24: Console.WriteLine(" ");
25: }
26: }
27: }

The following is the output:

          X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X

This listing maps out the Sin method. A for statement in Lines 12 to 25 loops through double values, incrementing them by .2 each iteration. The sine of this value is obtained using the Math.Sin method in Line 14. The sine is a value from 1.0 to 1.0. To make the display easier, this value is converted to a value from 10 to 10. This conversion is done by multiplying the returned sine value by 10 and then rounding the value with the Math.Round method.

The result of doing the multiplication and rounding is that val2 is a value from 10 to 10. A for loop in Line 15 displays a single line of characters. This line of characters is spaces, with the exception of the character in the position equal to val2. Line 24 prints another space to start a new line. The result of this work is a rough display of a sine curve.

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