Monads/Writer monad: Difference between revisions
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# Apply a composition of the Writer versions of root, addOne, and half to the integer 5, deriving both a value for the Golden Ratio φ, and a concatenated log of the function applications (starting with the initial value, and followed by the application of root, etc.) |
# Apply a composition of the Writer versions of root, addOne, and half to the integer 5, deriving both a value for the Golden Ratio φ, and a concatenated log of the function applications (starting with the initial value, and followed by the application of root, etc.) |
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=={{header|J}}== |
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Based on javascript implementation: |
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<lang J>root=: %: |
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incr=: >: |
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half=: -: |
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tostr=: ,@": |
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loggingVersion=: conjunction define |
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n;~u |
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) |
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Lroot=: root loggingVersion 'obtained square root' |
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Lincr=: incr loggingVersion 'added 1' |
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Lhalf=: half loggingVersion 'divided by 2' |
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loggingUnit=: verb define |
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y;'Initial value: ',tostr y |
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) |
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loggingBind=: adverb define |
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r=. u 0{::y |
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v=. 0{:: r |
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v;(1{::y),LF,(1{::r),' -> ',tostr v |
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) |
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loggingCompose=: dyad define |
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;(dyad def '<x`:6 loggingBind;y')/x,<loggingUnit y |
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)</lang> |
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Task example: |
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<lang J> 0{::Lhalf`Lincr`Lroot loggingCompose 5 |
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1.61803 |
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1{::Lhalf`Lincr`Lroot loggingCompose 5 |
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Initial value: 5 |
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obtained square root -> 2.23607 |
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added 1 -> 3.23607 |
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divided by 2 -> 1.61803</lang> |
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=={{header|JavaScript}}== |
=={{header|JavaScript}}== |
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