asmhatreandClaude Sonnet 5
f59c1de96d
Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01B38FGKKam5SCGgwgduVAh3
29 lines
1.2 KiB
Plaintext
29 lines
1.2 KiB
Plaintext
$ java --enable-preview PrimitivePatterns (JDK 27)
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--- instanceof <primitive>: an exact-conversion test, not a cast
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100 instanceof byte = true
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300 instanceof byte = false (a byte holds -128..127)
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CHECK ok : 100 converts to byte exactly, 300 does not
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binding: byte narrow = 100
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16_777_216 instanceof float = true
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16_777_217 instanceof float = false (float has a 24-bit significand)
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CHECK ok : int to float is exact up to 2^24 and lossy after
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--- switch on a long, with pattern labels and a guard
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classify(0) = zero
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classify(1) = one
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classify(-7) = negative (-7)
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classify(9000000000) = positive (9000000000)
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CHECK ok : long switch dispatches on constants, then patterns
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--- switch on an Object: an Integer matches 'case int'
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describe(Integer 7) = an int 7
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describe(Integer 5000) = a large int 5000
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describe(Long 7) = a long 7
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describe(Double 2.5) = a double 2.5
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describe(String hello) = a String of length 5
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describe(Character x) = something else: x
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CHECK ok : an Integer 5000 matches case int with a guard
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--- record pattern with a narrowing primitive component
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Reading[celsius=36] -> fits in a byte: 36
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Reading[celsius=4000] -> needs a full int: 4000
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CHECK ok : Reading(byte c) matches 36 but not 4000
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exit=0
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