worked example: big-numbers-to-words

    description:
        convert integers into English words

    code:
        ones |1> => |one>
        ones |2> => |two>
        ones |3> => |three>
        ones |4> => |four>
        ones |5> => |five>
        ones |6> => |six>
        ones |7> => |seven>
        ones |8> => |eight>
        ones |9> => |nine>

        tens |10> => |ten>
        tens |11> => |eleven>
        tens |12> => |twelve>
        tens |13> => |thirteen>
        tens |14> => |fourteen>
        tens |15> => |fifteen>
        tens |16> => |sixteen>
        tens |17> => |seventeen>
        tens |18> => |eighteen>
        tens |19> => |nineteen>

        ten |20> => |twenty>
        ten |30> => |thirty>
        ten |40> => |forty>
        ten |50> => |fifty>
        ten |60> => |sixty>
        ten |70> => |seventy>
        ten |80> => |eighty>
        ten |90> => |ninety>

        tens |*> #=> smerge[" "] sdrop ( ten times-by[10] int-divide-by[10] |_self> . ones mod[10] |_self> )
        hundreds-rule |*> #=> smerge[" and "] (hundreds int-divide-by[100] mod[1000] |_self> . tens mod[100] |_self>)

        hundreds |0> #=> |>
        hundreds |*> #=> ones |_self> __ |hundred>

        thousands |0> #=> |>
        thousands |*> #=> hundreds-rule |_self> __ |thousand>

        millions |0> #=> |>
        millions |*> #=> hundreds-rule |_self> __ |million>

        billions |0> #=> |>
        billions |*> #=> hundreds-rule |_self> __ |billion>

        trillions |0> #=> |>
        trillions |*> #=> hundreds-rule |_self> __ |trillion>

        op |seq> => |op: hundreds-rule> . |op: thousands> . |op: millions> . |op: billions> . |op: trillions>

        n2w |0> => |zero>
        n2w |*> #=> smerge[", "] sreverse op-zip(op |seq>, split-num |_self>)

        split-num |*> #=> process-if if(is-less-than[1000] |_self>, |less than 1000:> __ |_self>, |greater than 1000:> __ |_self>)
        process-if |less than 1000: *> #=> remove-leading-category |_self>
        process-if |greater than 1000: *> #=> mod[1000] remove-leading-category |_self> . split-num int-divide-by[1000] remove-leading-category |_self>

    examples:
        n2w |123456789012345>
            |one hundred and twenty three trillion, four hundred and fifty six billion, seven hundred and eighty nine million, twelve thousand, three hundred and forty five>

    source code:
        load big-numbers-to-words.sw
      
    see also:
        numbers-to-words      

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