# Difference between revisions of "LOG"

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− | * Value parameter MUST be greater than 0! | + | * Value parameter MUST be greater than 0! [[ERROR Codes|"Illegal function call" error]] using negative or zero values! |

* The natural logarithm is the logarithm to the base '''e = 2.718282''' (approximately). | * The natural logarithm is the logarithm to the base '''e = 2.718282''' (approximately). | ||

* The natural logarithm of ''a'' is defined as the integral from 1 to ''a'' of dx/x. | * The natural logarithm of ''a'' is defined as the integral from 1 to ''a'' of dx/x. | ||

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{{CodeStart}} | {{CodeStart}} | ||

− | FUNCTION Log10#(value AS DOUBLE) | + | FUNCTION Log10#(value AS DOUBLE) {{Cl|STATIC}} |

Log10# = LOG(value) / LOG(10.#) | Log10# = LOG(value) / LOG(10.#) | ||

END FUNCTION | END FUNCTION | ||

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{{CodeEnd}} | {{CodeEnd}} | ||

− | :''Explanation:'' The natural logarithm of the value is divided by the base 10 logarithm. The LOG of ten is designated as a DOUBLE precision return by using # after the Log10 value. | + | :''Explanation:'' The natural logarithm of the value is divided by the base 10 logarithm. The LOG of ten is designated as a DOUBLE precision return by using # after the Log10 value. The return tells you the number of times 10 goes into a value. |

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{{CodeStart}} | {{CodeStart}} | ||

− | FUNCTION | + | FUNCTION BIN$ (n&) |

− | FOR p% = 0 TO {{Cl|LOG}}(n& + .1) | + | IF n& < 0 THEN EXIT FUNCTION 'positive numbers only! negative error! |

− | + | FOR p% = 0 TO INT({{Cl|LOG}}(n& + .1) / {{Cl|LOG}}(2)) ' added +.1 to get 0 to work | |

− | NEXT p% | + | IF n& {{Cl|AND}} 2 ^ p% THEN s$ = "1" + s$ ELSE s$ = "0" + s$ 'find bits on |

− | IF s$ = "" THEN | + | NEXT p% |

+ | IF s$ = "" THEN BIN$ = "&B0" ELSE BIN$ = "&B" + s$ 'check for zero return | ||

END FUNCTION | END FUNCTION | ||

{{CodeEnd}} | {{CodeEnd}} | ||

− | : ''Explanation:'' The LOG of | + | : ''Explanation:'' The LOG of a '''positive''' [[INTEGER]] value is divided by the LOG of 2 to determine the number of binary digits that will be returned. The FOR loop compares the value with the exponents of two and determines if a bit is ON or OFF as "1" or "0". |

## Revision as of 21:17, 13 July 2010

The **LOG** math function returns the natural logarithm of a specified numerical value.

*Syntax:* logarithm = LOG(value)

- Value parameter MUST be greater than 0! "Illegal function call" error using negative or zero values!
- The natural logarithm is the logarithm to the base
**e = 2.718282**(approximately). - The natural logarithm of
*a*is defined as the integral from 1 to*a*of dx/x. - Returns are default SINGLE precision unless the value parameter uses DOUBLE precision.

*Example 1:* FUNCTION to find the base ten logarithm of a numerical value.

FUNCTION Log10#(value AS DOUBLE) STATIC Log10# = LOG(value) / LOG(10.#) END FUNCTION

*Explanation:*The natural logarithm of the value is divided by the base 10 logarithm. The LOG of ten is designated as a DOUBLE precision return by using # after the Log10 value. The return tells you the number of times 10 goes into a value.

*Example 2:* A binary FUNCTION to convert INTEGER values using LOG to find the number of digits the return will be.

FUNCTION BIN$ (n&) IF n& < 0 THEN EXIT FUNCTION 'positive numbers only! negative error! FOR p% = 0 TO INT(LOG(n& + .1) / LOG(2)) ' added +.1 to get 0 to work IF n& AND 2 ^ p% THEN s$ = "1" + s$ ELSE s$ = "0" + s$ 'find bits on NEXT p% IF s$ = "" THEN BIN$ = "&B0" ELSE BIN$ = "&B" + s$ 'check for zero return END FUNCTION

*Explanation:*The LOG of a**positive**INTEGER value is divided by the LOG of 2 to determine the number of binary digits that will be returned. The FOR loop compares the value with the exponents of two and determines if a bit is ON or OFF as "1" or "0".

*See also:*

*Navigation:*