Difference between revisions of "Thunks and Streams Assignment"

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==Stream Utilities==
 
==Stream Utilities==
  
 +
===plausible-stream?===
 
define a function <code>plausible-stream?</code> which returns #t if the specified parameter is a thunk which when invoked returns a pair whose cdr is a thunk, #f otherwise.
 
define a function <code>plausible-stream?</code> 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 <code>plausible-stream?</code> recursively on the <code>cdr</code>?
 
WARNING: what could happen if you called <code>plausible-stream?</code> recursively on the <code>cdr</code>?
  
 +
===next-value-from-stream===
 
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.
  
 +
===next-stream-from-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>next-stream-from-stream</code> which takes a stream parameter and returns the next stream of that stream.
  
 +
===stream-cons===
 
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:
 
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:
  

Revision as of 18:09, 2 July 2019

Code To Use

define-syntax

lambda

procedure?

procedure-arity

pair?

cons

car

cdr

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-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))

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...