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epxt() calculates wrong results - same with pow(), same with ** operator

Volker T

I ran a test script using the expt() function, and it gave odd results.

So I typed it directly into CIW command line:

expt(10 12)

=> -727379968

I would expect the answer to be 1000000000000.

It works for a power of 9, though:

expt(10 9)

=> 1000000000

Same happens with other exponents:

for(i -24 24 printf("%g\n" 1.0*expt(10 i)) )

=>

1e-24
1e-23
1e-22
1e-21
1e-20
1e-19
1e-18
1e-17
1e-16
1e-15
1e-14
1e-13
1e-12
1e-11
1e-10
1e-09
1e-08
1e-07
1e-06
1e-05
0.0001
0.001
0.01
0.1
1
10
100
1000
10000
100000
1e+06
1e+07
1e+08
1e+09
1.41007e+09
1.21575e+09
-7.2738e+08
1.31613e+09
2.76447e+08
-1.53049e+09
1.87492e+09
1.56933e+09
-1.48662e+09
-1.98128e+09
1.66199e+09
-5.5994e+08
-1.30443e+09
-1.59384e+08
-1.59384e+09

By the way: 10**12 is also -727379968 accoring to CIW...

Is there a bug?

Parents Reply Children
  • in reply to ebecheto

    Thank you very much!

    I thought I had also tested with expt(10 1.0*i) in my loop and got the same result, but apparently I forgot to save my code before testing again, so no wonder, the same unexpected results came out.

    I checked again, this time with expt(10 1.0*i) and a saved file and it works as expected.

  • in reply to Volker T

    Rather than using 1.0*I you can also do float(i) to cast an integer to a float. Or if you just use expt(10.0 i) that would work too. Provided that one of the numbers is a float, it would be fine.

    Andrew

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