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Mutual recursion: Difference between revisions
→{{header|Lambdatalk}}
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Line 1,494:
{map M {serie 0 19}}
-> 0 0 1 2 2 3 4 4 5 6 6 7 7 8 9 9 10 11 11 12
</lang>
The naïve version is very slow, {F 80} requires 3800 ms on a recent laptop, so let's memoize:
<lang scheme>
{def cache
{def cache.F {#.new}}
{def cache.M {#.new}}
{lambda {:f :n}
{let { {:f :f} {:n :n}
{:cx {if {equal? :f MF}
then {cache.F}
else {cache.M}}}
} {if {equal? {#.get :cx :n} undefined}
then {#.get {#.set! :cx :n {:f :n}} :n}
else {#.get :cx :n}}}}}
-> cache
{def MF
{lambda {:n}
{if {= :n 0}
then 1
else {- :n {MM {cache MF {- :n 1}}}}}}}
-> MF
{def MM
{lambda {:n}
{if {= :n 0}
then 0
else {- :n {MF {cache MM {- :n 1}}}}}}}
-> MM
{MF 80}
-> 50 (requires 55 ms)
{map MF {serie 0 100}} (requires75ms)
-> 1 1 2 2 3 3 4 5 5 6 6 7 8 8 9 9 10 11 11 12 13 13 14 14 15 16 16 17 17
18 19 19 20 21 21 22 22 23 24 24 25 25 26 27 27 28 29 29 30 30 31 32 32
33 34 34 35 35 36 37 37 38 38 39 40 40 41 42 42 43 43 44 45 45 46 46 47
48 48 49 50 50 51 51 52 53 53 54 55 55 56 56 57 58 58 59 59 60 61 61 62
</lang>
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