From QB64 Wiki
The LOG math function returns the natural logarithm of a specified numerical value.
- 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".