Difference between revisions of "Thunks and Streams Assignment"
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=Stream Utilities= | =Stream Utilities= | ||
| − | define a function <code>stream?</code> which returns #t if the specified parameter is a | + | define a function <code>plausible-stream?</code> which returns #t if the specified parameter is a thunk which evaluates to a pair whose cdr is a thunk, #f otherwise. |
| + | |||
| + | WARNING: what could happen if you called <code>plausible-stream?</code> recursively on the <code>cdr</code>? | ||
define a function <code>next-value-from-stream</code> which takes a stream parameter and returns the next value of that stream. | define a function <code>next-value-from-stream</code> which takes a stream parameter and returns the next value of that stream. | ||
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define a function <code>next-stream-from-stream</code> which takes a stream parameter and returns the next stream of that stream. | define a function <code>next-stream-from-stream</code> which takes a stream parameter and returns the next stream of that stream. | ||
| − | define a function <code>stream-cons</code> which takes two parameters <code>value</code> and <code>stream-prime</code>. if the specified <code>stream-prime</code> parameter is not a | + | define a function <code>stream-cons</code> which takes two parameters <code>value</code> and <code>stream-prime</code>. if the specified <code>stream-prime</code> parameter is not a thunk then an error should be raised: |
| + | |||
| + | <code>(raise (error "not a thunk" stream-prime))</code> | ||
| − | + | WARNING: what could happen if you called <code>plausible-stream?</code> on <code>stream-prime</code>? | |
=Stream App= | =Stream App= | ||
define <code>flip-flop-stream</code> which produces #t #f #t #f #t #f #t #f... | define <code>flip-flop-stream</code> which produces #t #f #t #f #t #f #t #f... | ||
Revision as of 15:51, 2 July 2019
Thunk Utilities
define a function thunk? which returns #t if the specified parameter is a thunk, #f otherwise.
define a macro thunk which creates thunk
define a function dethunk which takes a thunk parameter th and returns the result of invoking th.
Stream Utilities
define a function plausible-stream? which returns #t if the specified parameter is a thunk which evaluates to a pair whose cdr is a thunk, #f otherwise.
WARNING: what could happen if you called plausible-stream? recursively on the cdr?
define a function next-value-from-stream which takes a stream parameter and returns the next value of that stream.
define a function next-stream-from-stream which takes a stream parameter and returns the next stream of that stream.
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))
WARNING: what could happen if you called plausible-stream? on stream-prime?
Stream App
define flip-flop-stream which produces #t #f #t #f #t #f #t #f...
