p6rt
commented
8 years ago From @zoffixznet
*** Note: I started writing this, but when I got to uint8, I realized it was taking too much time, so I gave up; this is a partial report*** ********************************************************************************************************************************************
There are some inconsistencies with the behaviours among the native types, including buggy behaviour of postdecrement/increment ops when the increment/decrement would make underflow/overflow occur.
Here's the summary table. Detailed code executes are in the attachment.
The meaning of headers: Assigning Too-Low Value: assigning value below one a type can hold, such as -1 to an unsigned type Assigning Too-High Value: same as above, except too high a value, such as a 50-bit value into int32 Underflow works: decrementing past lowest value flips over to the other end, such as decrementing a 0 on uint8 gives 256 Overflow works: same as above, except on the upper bounder, such as incrementing 256 on uint8 gives 0 Post-[de/in]cremnent on overflow works: best shown in an example:
WORKS: we flipped over the boundary and increment/decrement operation happened just once, returning the unmodified value in the second say():
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BROKEN: operation happens TWICE and second say() behaves as if it were a prefix increment/decrement:
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And here's the table showing the results of my evaluation:
[Type] [Assigning Too-Low Value] [Assigning Too-High Value] [Underflow works] [Overflow works] [Post-[de/in]crement on overflow works] int Runtime error Runtime error Yes Yes Yes int8 Value=0 Value=0 Yes Yes NO int16 Value=0 Value=0 Yes Yes NO int32 Value=0 Value=0 Yes Yes NO int64 Runtime error Runtime error Yes Yes Yes uint Behaves as int Behaves as int No (behaves as int) No (behaves as int) Yes (but behaves as int) uint8 Value rolls over Value rolls over No $x -= 1 works, but No $x +=1 work, but --$x gives negatives ++$x goes over 255
byte uint16 uint32 uint64 num num32 num64
Migrated from rt.perl.org#127409 (status was 'new')
Searchable as RT127409$