Mauer-Oats Classes > Intermediate CS > 22a. Recursion > 22a. More Recursion

22a. More Recursion

sum-cubes: number(n) -> number. Finds the sum of the first n perfect cubes.
vblock: number(n) image(img) -> image. Makes a vertical stack of n copies of img.
hblock: number(n) image(img) -> image. Make a horizontal stack of n copies of img.
grid: number(rows) number(columns) image -> image. Make a grid that is columns wide and rows tall of the image repeated.
add-sqrt: number(start) number(end) -> number. Add up (sqrt n) for every integer n with start <= n <= end If no numbers fit this description, the sum should be zero.

Example: when start=4 and end=5, the answer is (+ (sqrt 4) (sqrt 5)), which is about 4.236.
```
(check-expect (add-sqrt 4 3) 0)
(check-expect (add-sqrt 4 4) 2)
(check-within (add-sqrt 4 5) 4.23 0.01)
(check-within (add-sqrt 4 8) 12.15 0.01)
```
lots-of-hyphens: string(word) -> string. Insert a hyphen after every letter in the word.
```
(lots-of-hyphens "grape") ==> "g-r-a-p-e-"
```
Extra: get "g-r-a-p-e" instead.
ten-circle: number(start) number(end) -> image. Produces concentric circles starting at radius start and drawing every 10 units until the radius is at least end. Assume start < end.