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>


n2w |0> => |zero>

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