Difference between revisions of "LOG"

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[[EXP]], [[&B]] (binary number)
[[EXP]], [[&B]] (binary number)
[http://qb64.net/wiki/index.php?title=Mathematical_Operations#Derived_Mathematical_Functions Derived Trigonometric Functions]

Revision as of 23:56, 28 September 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:

EXP, &B (binary number)

Derived Trigonometric Functions

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