| <range> | (<seq.>) | C | 
| range-by | (from|<num> test|<fun> lim|<num> by|<fun>=> <range>) | G | 
|  | returns a range starting from, updated with by,
  and continuing until (test x lim) is false. |  | 
| range | (from|<num> test|<fun> lim|<fun> => <range>) | G | 
|  | ==  (range-by from test lim (op + _ 1)) |  | 
| from | (from|<num> => <range>) | G | 
|  | ==  (range from (always #t) 0) |  | 
| below | (lim|<num> => <range>) | G | 
|  | ==  (range 0 < lim) |  | 
| <step> | (<seq.>) | C | 
|  | Steps represent step functions. |  | 
| first-then | (first|<fun> then|<fun> => <step>) | G | 
|  | returns a new step object, calling thunks first to retrieve
initial value and then to retrieve subsequent values. |  | 
| each | (f|<fun> => <each>) | G | 
|  | returns a new each object, calling f thunk to retrieve
  each value. |  | 
| <cycle> | (<seq.>) | C | 
|  | Cycles provide a mechanism to create infinite sequences repeating
  a certain sequence over and over again. |  | 
| cycle | (x|... => <cycle>) | G | 
|  | returns a cycles that repeats elements of x. |  | 
|  |