Practical numbers: Difference between revisions
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→Using Srinivasan-Stewart-Sierpinsky characterization: 2 other benchmarks
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=={{header|RPL}}==
{{works with|HP|49/50}}
« 1 SF REVLIST
1 « '''IF''' 1 FS? '''THEN''' NOT '''IF''' DUP '''THEN''' 1 CF '''END END''' » DOLIST
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» '<span style="color:blue">PRACTICAL?</span>' STO <span style="color:grey">@ ( n → boolean ) </span>
From [https://en.wikipedia.org/wiki/Practical_number#Characterization_of_practical_numbers the Wikipedia article]. It's very fast and needs only to store the prime decomposition of the tested number.
« '''CASE'''
DUP LN 2 LN / FP NOT '''THEN''' SIGN '''END''' <span style="color:grey">@ powers of two are practical</span>
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PICK3 j GET ^ *
-2 '''STEP'''
DROP2 2 FS?
'''END'''
» '<span style="color:blue">PRACTICAL?</span>' STO <span style="color:grey">@ ( n → boolean ) </span>
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1: 0
</pre>
Non-practicality of 66666 is established in 0.57 seconds on an HP-50 handheld calculator; testing 222222 or 9876543210 needs 1.5 seconds. Because of the algorithm's efficiency, even antique calculators from the 1970s could implement it, with an acceptable execution time.
=={{header|Rust}}==
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