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Compare to '=' for floating point figures
Tip-No.: 2541 ( INFO2541 )

Short text

Compare to '=' for floating point figures
Tip-No.: 2541

Symptom

Two floating point numbers should be equal or appear "equal" (e.g.
after WRITE), but the = test has not been met.

Cause

Due to fundamentally occurring rounding errors in F-arithmatic, the
last digits (those furthest to the right) are often not exaxt. This
is not only true for the result of long invoices, but also if an
operand has come from a different data type via conversion.

Solution

It often makes more sense to test whether the relative error is less
than the appropriate error margin instead of testing for equality.
Therefore:
-e <= ( F - G ) / G <= e.