Because maybe most of you think I'm seeing white mice here I made a
testcase. I got the values a and b from an existing FlapTab morph in an
3.7alpha image.

Alex

| a b tab |
"Create a float close to  466.700581395349"
a _ (1.1 at: 1 put: 1081944885; at: 2 put: 2497074009; yourself).
b _ 105.
a + b - a = b. "This evaluates to false"

tab _ Flaps newFlapTitled: 'Test' onEdge: #top.
tab left: a.
"next line will run into an infinite loop"
tab extent: b at b