Difference between revisions of "Thunks and Streams Assignment"
| Line 50: | Line 50: | ||
<code>(raise (error "not a thunk" stream-prime))</code> | <code>(raise (error "not a thunk" stream-prime))</code> | ||
| − | If <code>stream-prime</code> is a thunk it should simply cons <code>value</code> and <code>stream-prime</code>. Do '''NOT''' create a thunk. | + | If <code>stream-prime</code> is a thunk it should simply [https://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cons%29%29 cons] <code>value</code> and <code>stream-prime</code>. Do '''NOT''' create a thunk. |
WARNING: what could happen if you called <code>plausible-stream?</code> on <code>stream-prime</code>? | WARNING: what could happen if you called <code>plausible-stream?</code> on <code>stream-prime</code>? | ||
Revision as of 03:44, 9 July 2019
Contents
Code To Use
Code To Implement
Thunk Utilities
thunk?
define a function thunk? which returns #t if the specified parameter is a thunk, #f otherwise.
thunk MACRO
define a macro thunk which creates thunk
dethunk
define a function dethunk which takes a thunk parameter th and returns the result of invoking th.
Stream Utilities
plausible-stream?
define a function plausible-stream? which returns #t if the specified parameter is a thunk which when invoked returns a pair whose cdr is a thunk, #f otherwise.
WARNING: what could happen if you called plausible-stream? recursively on the cdr?
next-value-from-stream
define a function next-value-from-stream which takes a stream parameter and returns the next value of that stream.
next-stream-from-stream
define a function next-stream-from-stream which takes a stream parameter and returns the next stream of that stream.
stream-next
BONUS method not officially part of the studio but a good idea.
define a function stream-next which takes a stream parameter and returns a pair of values for the next value and the next stream.
stream-cons
define a function stream-cons which takes two parameters value and stream-prime. if the specified stream-prime parameter is not a thunk then an error should be raised:
(raise (error "not a thunk" stream-prime))
If stream-prime is a thunk it should simply cons value and stream-prime. Do NOT create a thunk.
WARNING: what could happen if you called plausible-stream? on stream-prime?
Stream App
flip-flop-stream
define flip-flop-stream which produces #t #f #t #f #t #f #t #f...
