log (Function)

This function will calculate the natural logarithm of the argument.

Note: This function works with DOUBLE, but can also work with FLOAT as described in the Floating-point math introductory section.

Input:

V : DOUBLE

Value.

Returns: DOUBLE

The natural logarithm of V. If the value is 0, -Infinity is returned. If the value is less than 0, NaN is returned.

Declaration:

FUNCTION log : DOUBLE;
VAR_INPUT
v : DOUBLE;
END_VAR;

Example:

INCLUDE rtcu.inc
INCLUDE math.inc
 
PROGRAM test;
 
DebugMsg( message := "  log(100) = " + doubleToStr(v := log( v:= 100.0)));
DebugMsg( message := " log2(100) = " + doubleToStr(v := log2( v:= 100.0)));
DebugMsg( message := "log10(100) = " + doubleToStr(v := log10( v:= 100.0)));
 
END_PROGRAM;