Q(uick)BASIC Function: LOG
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LOG
A math function that returns the natural logarithm of a numeric expression
Worth knowing
Useful and cross-version information about the programming environments of QBasic and QuickBasic.
Syntax
- EXP(numeric-expression)
- LOG(numeric-expression)
Description/Parameter(s)
numeric-expression | For EXP, a number less than or equal to 88.02969. For LOG, any positive numeric expression. |
Example
PRINT EXP(0), EXP(1) 'Output is: 1 2.718282
PRINT LOG(1), LOG(EXP(1)) 'Output is: 0 1
Syntax
- LOG(numeric-expression)
Description/Parameter(s)
The numeric expression, n, must be greater than zero.
The natural logarithm is the logarithm to the base e. The constant e is approximately equal to 2.718282.
The LOG function calculates the natural logarithm with single- precision accuracy, unless the argument n is a double-precision value. In this case LOG is calculated with double-precision accuracy.
You may calculate base-10 logarithms by dividing the natural logarithm of the number by the logarithm of 10. The following FUNCTION calculates base-10 logarithms:
- FUNCTION Log10(X) STATIC
- Log10=LOG(X)/LOG(10.#)
- END FUNCTION
Example
This example prints the value of e and then prints the natural logarithms of e taken to the first, second, and third powers.
CLS ' Clear screen
PRINT EXP(1),
FOR I = 1 TO 3
PRINT LOG(EXP(1) ^ I),
NEXT
Sample Output:
2.718282 1 2 3See also:
Syntax
- LOG(numeric-expression)
Description/Parameter(s)
The argument numeric-expression must be greater than zero.
Usage Notes
- LOG is calculated in single precision if numeric-expression is an integer or single-precision value. If you use any other numeric data type, LOG is calculated in double-precision.
- The natural logarithm is the logarithm to the base e. The constant e is approximately equal to 2.718282.
- You can calculate base-10 logarithms by dividing the natural logarithm of the number by the natural logarithm of 10. The following FUNCTION procedure calculates base-10 logarithms:
- FUNCTION Log10 (X) STATIC
- Log10 = LOG(X) / LOG(10#)
- END FUNCTION
Example
This example prints the value of e and uses the LOG function to calculate the natural logarithm of e taken to the first, second, and third powers.
CLS 'Clear screen.
PRINT EXP(1),
FOR I = 1 TO 3
PRINT LOG(EXP(1) ^ I),
NEXT
Sample Output:
2.718282 1 2 3See also: