Giving a True when it should be nil

[marc_pepin]

I got a routine with the line (/= (nth 4 item) 1.5) which return "T" for every real that (nth 4 item)  return even 1.5???

Does anyone ever experience that?

[dbhunia]

Hi

if (nth 4 item)  return 1.5???  (say 1.55555)

then (/= (nth 4 item) 1.5) means (/= 1.55555 1.5) always return "T"

[marko_ribar · Accepted solution]

Your (nth 4 item) is not exactly 1.5... Check it with (rtos (nth 4 item) 2 50)... If it returns some numbers after 1.5, then your check is wrong, try changing it to (not (equal (nth 4 item) 1.5 fuzz))... If number from (nth 4 item) is in the fuzz range near 1.5 this fix should return valid check value - nil (not T)...

[Kent1Cooper · Accepted solution]

One of your values that displays as 1.5 may actually be 1.499999999999308 or 1.50000000000276 or something.  Comparing real numbers, which can result from various kinds of calculations and extractions that can have such tiny differences, should be done using the (equal) function with a fuzz factor:

(not (equal (nth 4 item) 1.5 1e-6))

[cadffm]

They are not the same..

(Rtos (nth 4 item) 2 15) , is it 1.500000000000000 ?

Use function equal [F1]

[Kent1Cooper]

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@marko_ribar wrote:

.... (rtos (nth 4 item) 2 50) ....

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[Don't bother with asking for 50 decimal places.  16 is the most you're ever going to wring out of it.]