57 lines
1.4 KiB
Markdown
57 lines
1.4 KiB
Markdown
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# primrec
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Basis Function Combinator
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From the \"Overview of the language JOY\":
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\> The primrec combinator expects two quoted programs in addition to a
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data parameter. For an integer data parameter it works like this: If the
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data parameter is zero, then the first quotation has to produce the
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value to be returned. If the data parameter is positive then the second
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has to combine the data parameter with the result of applying the
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function to its predecessor.:
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5 [1] [*] primrec
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\> Then primrec tests whether the top element on the stack (initially
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the 5) is equal to zero. If it is, it pops it off and executes one of
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the quotations, the \[1\] which leaves 1 on the stack as the result.
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Otherwise it pushes a decremented copy of the top element and recurses.
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On the way back from the recursion it uses the other quotation, \[\*\],
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to multiply what is now a factorial on top of the stack by the second
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element on the stack.:
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n [Base] [Recur] primrec
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0 [Base] [Recur] primrec
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------------------------------
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Base
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n [Base] [Recur] primrec
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------------------------------------------ n > 0
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n (n-1) [Base] [Recur] primrec Recur
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Gentzen diagram.
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## Definition
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if not basis.
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## Derivation
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if not basis.
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## Source
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if basis
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## Discussion
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Lorem ipsum.
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## Crosslinks
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Lorem ipsum.
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