LGF_CompareLReal (FC / 3.0.2)

Author: Siemens Digital Industry

Short description

This function checks floating point numbers for equality, by using an approximation formula and a fixed precision by constant 1.0E-12 (pico)

Block Interface


LReal	valueA	Ret_Val	Bool
LReal	valueA	Ret_Val	Bool
LReal	valueB
LReal	valueB

Input parameter

Identifier	Data type	Description
valueA	LReal	First LREAL number to be compared.
valueB	LReal	Second LREAL number to be compared.

Output parameter

Identifier	Data type	Description
Ret_Val	Bool	FALSE: not equal TRUE: approximately the same

Functional description

The comparison of the LREAL numbers is based on an fixed accuracy of 1.0E-12. The difference between the two input values must be smaller than the PRECISION accuracy multiplied by one of the two input values.

Equation:

result := FALSE OR ((#valueA = 0.0) AND (ABS(#valueB) <= #precision)) OR ((#valueB = 0.0) AND (ABS(#valueA) <= #precision)) OR (ABS(valueA - valueB) <= (PRECISION * ABS(valueA));

Note: If your application requires a different accuracy when comparing the numbers, adapt the “PRECISION” constant in the function to your requirements.; Or you may use the FC LGF_CompareLRealByPrecision.

Change log

Version & Date		Change description
	1.0.0	Siemens Industry Online Support
	13.01.2017	First released version
	1.0.1	Siemens Industry Online Support
	17.08.2018	Upgrade: TIA V15 Update 2
	1.0.2	Siemens Industry Online Support
	23.11.2018	Upgrade: TIA V15.1
	1.0.3	Simatic Systems Support
	03.06.2019	Refactoring and performance improvment Delete Error and Status there is no need for, because of changed / adjusted algorithm add eno handling
	3.0.0	Simatic Systems Support
	23.04.2020	Set version to V3.0.0, harmonize the version of the whole library
	3.0.1	Simatic Systems Support
	19.01.2020	Insert documentation
	3.0.2	Simatic Systems Support
	21.12.2023	Fix compare error if one value is exactly zero