8 lines
194 B
Smalltalk
8 lines
194 B
Smalltalk
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Number extend [
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my_factorial [
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self < 0 ifTrue: [ self error: 'my_factorial is defined for natural numbers' ].
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self isZero ifTrue: [ ^1 ].
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^self * ((self - 1) my_factorial)
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]
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].
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