scala-exercises | The easy way to learn Scala | Functional Programming library
kandi X-RAY | scala-exercises Summary
kandi X-RAY | scala-exercises Summary
The easy way to learn Scala.
Support
Quality
Security
License
Reuse
Top functions reviewed by kandi - BETA
Currently covering the most popular Java, JavaScript and Python libraries. See a Sample of scala-exercises
scala-exercises Key Features
scala-exercises Examples and Code Snippets
Community Discussions
Trending Discussions on scala-exercises
QUESTION
I want to understand what does second argument in indexOf
in Scala mean for Strings?
ANSWER
Answered 2021-Dec-01 at 10:45According to Scala String documentation, the second parameter is the index to start searching from:
QUESTION
The variety of books, articles, blog posts suggests that rewriting recursive function into tail recursive function makes it faster. No doubts it is faster for trivial cases like generating Fibonacci numbers or calculating factorial. In such cases there is a typical approach to rewrite - by using "helper function" and additional parameter for intermediate results.
TAIL RECURSION is the great description of the differences between tail recursive and not tail recursive functions and the possible way how to turn the recursive function into a tail recursive one. What is important for such rewriting - the number of function calls is the same (before/after rewriting), the difference comes from the way how those calls are optimized for tail recursion.
Nevertheless, it is not always possible to convert the function into tail recursive one with such an easy trick. I would categorize such cases as below
- Function still can be rewritten into tail recursive but that might require additional data structures and more substantial changes in the implementation
- Function cannot be rewritten into tail recursive with any means but recursion still can be avoided by using loops and imitating stack (I'm not 100% sure that tail recursion is impossible in some cases and I cannot describe how identify such cases, so if there is any academical research on this subject - the link would be highly appreciated)
Now let me consider specific example when function can be rewritten into tail recursive by using additional structures and changing the way algorithm works.
Sample task: Print all sequences of length n containing 1 and 0 and which do not have adjacent 1s.
Obvious implementation which comes to mind first is below (on each step, if current value is 0 then we generate two sequences with length n-1 otherwise we generate only sequence with length n-1 which starts from 0)
...ANSWER
Answered 2021-Oct-22 at 11:07The class of functions in 1 is empty: any computable function written in a recursive style has a tail-recursive equivalent (at the limit, since there's a tail-recursive implementation of a Turing Machine, you can translate any computable function into a Turing Machine definition and then the tail recursive version of that function is running that definition through the tail-recursive implementation of a Turing Machine).
There are likewise no functions for which tail recursion is intrinsically less efficient than non-tail recursion. In your example, for instance, it's simply not correct that "it's much more efficient in terms of memory because no additional data structures of intermediate results are required." The required additional structure of intermediate results is implicit in the call-stack (which goes away in the tail recursive version). While the call stack is likely an array (more space efficient than a linked-list) it also, because of its generality, stores more data than is required.
QUESTION
I am trying to understand the traverse for list using this page, https://www.scala-exercises.org/cats/traverse
and I have a very basic question (sorry for those who think it is too easy or obvious). just check below signature
...ANSWER
Answered 2020-Nov-11 at 13:57Because if you have (n+1)-parameter method foo
QUESTION
I just started with scala and want to build a connection to my DB.
(My knowledge stems from the scala/doobie Tutorial's on https://www.scala-exercises.org/)
Now here is the Code:
...ANSWER
Answered 2020-Feb-14 at 14:21The problem that compiler cant find ContextShift[IO]
instance in implicit scope, which is required for some of methods (not sure which exactly).
You need to declare your own in implicit scope, like
Community Discussions, Code Snippets contain sources that include Stack Exchange Network
Vulnerabilities
No vulnerabilities reported
Install scala-exercises
Support
Reuse Trending Solutions
Find, review, and download reusable Libraries, Code Snippets, Cloud APIs from over 650 million Knowledge Items
Find more librariesStay Updated
Subscribe to our newsletter for trending solutions and developer bootcamps
Share this Page