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fp2023:lab05 [2023/03/31 10:19]
pdmatei 		fp2023:lab05 [2023/03/31 12:58] (current)
pdmatei
Line 34: Line 34:
   def head: Int    def head: Int 
   def tail: OList   def tail: OList
-  def foldRight(acc: ​Int)(op: (Int,Int) => Int): Int+  def foldRight[B](acc: B)(op: (Int,B) => B): B 
 +  def foldLeft[B](acc:​ B)(op: (B,Int) => B): B
   def indexOf(i: Int): Int   def indexOf(i: Int): Int
   def filter(p: Int => Boolean): OList   def filter(p: Int => Boolean): OList
Line 48: Line 49:
 **4.2.2.** Implement ''​head''​ and ''​tail''​ accordingly. **4.2.2.** Implement ''​head''​ and ''​tail''​ accordingly.
  
-**4.2.3.** Implement ''​foldRight''​. Follow the same strategy as in the previous labs.+**4.2.3.** Implement ''​foldRight''​. Follow the same strategy as in the previous labs. Also implement foldLeft. Make sure it is tail-recursive.
  
-**4.2.4.** Implement ''​indexOf''​ which retrieves the position of an element in a list if it exists and -1 otherwise. Try and use ''​foldRight''​ for your implementation. 
  
-**4.2.5.** Implement ''​filter''​. Try and use ''​foldRight''​ in your implementation. The following diagram illustrates the behaviour of filter:+**4.2.5.** Implement ''​filter''​. Try and use ''​foldRight''​ in your implementation. The following diagram illustrates the behaviour of ''​filter''​:
 <​code>​ <​code>​
    1 2 3 4 5 6 7 8 9 10 11    1 2 3 4 5 6 7 8 9 10 11
Line 59: Line 59:
 </​code>​ </​code>​
  
-**4.2.6.** Implement ''​map''​. Try and use ''​foldRight''​ in your implementation. The following diagram illustrates the behaviour of map:+**4.2.4.** Implement ''​indexOf'' ​which retrieves the position of an element in a list if it exists and -1 otherwise. Try and use an appropriate type of fold for your implementation. 
 + 
 + 
 +**4.2.6.** Implement ​''​map''​. Try and use an appropriate type of fold in your implementation. The following diagram illustrates the behaviour of map:
 <​code>​ <​code>​
    1 2 3 4 5  6  7  8  9  10    1 2 3 4 5  6  7  8  9  10
Line 66: Line 69:
 </​code>​ </​code>​
  
-**4.2.7.** Implement ''​partition''​. It is supposed to return a pair of lists. (!!) Try and use ''​foldRight'' ​in your implementation. The following diagram illustrates the behaviour of partition:+**4.2.7.** Implement ''​partition''​. It is supposed to return a pair of lists. (!!) Try and use an appropriate type of fold in your implementation. The following diagram illustrates the behaviour of partition:
 <​code>​ <​code>​
    1 2 3 4 5 6 7 8 9 10    1 2 3 4 5 6 7 8 9 10
Line 80: Line 83:
 </​code>​ </​code>​
  
-**4.2.8.** Implement ''​forall''​. Try and use ''​foldRight'' ​in your implementation. The following diagram illustrates the behaviour of forall:+**4.2.8.** Implement ''​forall''​. Try and use an appropriate type of fold in your implementation. The following diagram illustrates the behaviour of forall:
 <​code>​ <​code>​
    1 2 3 4 5 6 7 8 9 10    1 2 3 4 5 6 7 8 9 10