Functional Programming The function Map() Today I would like to share last of small helper functions that help write concise code. Just like Apply, it helps to avoid null-checking ifs by conditionally applying a transformation function. Differently from Apply, it returns the result of the transformation, which, apparently, is quite a frequently used pattern. Let's
HackerRank Functional Challenges HR F#: Functions and Fractals: Sierpinski triangles The problem of drawing the Sierpinski triangles is considered to be advanced problem and it really is. The Sierpinski triangle is a fractal, constructed by recursively subdividing equilateral triangles into smaller equilateral triangles. If you ever played Deus Ex you may have noticed that its logo is inspired by the
HackerRank Functional Challenges HR F#: Pascal's Triangle The second problem from the Recursive subdomain is printing Pascal's Triangle for given n. Pascal's triangle is named after famous French mathematician from XVII century, Blaise Pascal. His findings on the properties of this numerical construction were published in this book, in 1665. Year before Great Fire of London. The
HackerRank Functional Challenges HR F#: Computing the GCD The greatest common divisor (or GCD) of two integers is the largest positive integer that divides two of these integers. The first of the Recursion problems on the Functional track at Hackerrank is computing the GCD using the Euclidean Algorithm. In this algorythm the largest from the pair is replaced
F# Quickstart WPF F#-only app in VSCode - Part 3 How to quickly create WPF F# project was shown in the first part. FsXaml and paket was added in the second part. This part will go reactive: add ReactiveUI and show how to update the view model asynchronously from F#. This part starts where the second part ends, from the
F# Quickstart WPF F#-only app in VSCode - Part 2 The first part shown how to create a WPF F# project with simple window and its view model, build this project and run it. Now lets add FsXaml using packet, use it to create types from XAML and create user control. All by directly modifying project files and run commands
HackerRank Functional Challenges HR F#: Compute the Area of a Polygon This is the last from the introductional problems in the Functional Programming domain on Hackerrank. This also might be most complicated among the introductionary problems: You are given the cartesian coordinates of a set of points in a 2D plane. When traversed sequentially, these points form a Polygon, P, which
HackerRank Functional Challenges HR F#: Compute the Perimeter of a Polygon The problem of computing perimeter of the polygon is one of the easy problems, but it requires a bit more programming. You are given the cartesian coordinates of a set of points in a 2D plane. When traversed sequentially, these points form a Polygon, P, which is not self-intersecting. Compute
HackerRank Functional Challenges HR F#: Functions or Not? The Functions or Not? problem is defined as follows: You are given a set of unique (x, y) ordered pairs constituting a relation. For each of these relations, identify whether they may possibly represent a valid function or not. On a new line for each test case, print YES if
HackerRank Functional Challenges HR F#: Lambda Calculus - Evaluating Expressions #2 The first λ-calculus evaluating expression problem was very easy. The second one is similar: Compute the value of (λx.x+1)((λy.y+2)3). Just to make a bit more fun from it, let's solve it by writing the code in F#: (fun x -> x + 1)((fun
HackerRank Functional Challenges HR F#: Lambda Calculus - Reductions #4 The last one from reduction problems is following: Reduce the following expression, using the beta-rule, to no more than one term. If the expression cannot be reduced, enter "CAN'T REDUCE". (λg.((λf.((λx.(f(xx)))(λx.(f(xx)))))g)) Well, now I (and you, if you follow) understand
HackerRank Functional Challenges HR F#: Lambda Calculus - Reductions #3 The third λ-calculus problem is a bit more advanced (although still simple): Reduce the following expression, using the beta-rule, to no more than one term. If the expression cannot be reduced, enter "CAN'T REDUCE". ((λx.(x x)) (λx.(x x))) "beta-reduction" is just recution by substituting
HackerRank Functional Challenges HR F#: Lambda Calculus - Reductions #2 The second λ-calculus problem is following: Reduce the following to no more than one term. If the expression cannot be reduced, enter "CAN'T REDUCE". ((λx.((λy.(x y)) x)) (λz.w)) Let's reduce the expressions: Framing parentheses are not required: (λx.((λy.(x y)) x)) (λz.w) Rewrite
HackerRank Functional Challenges HR F#: Lambda Calculus - Reductions #1 The Lambda Calculus - Reductions #1 is rather unusual. Instead of submitting the code, the required submission is a shortening of the lambda-expression. Reduce the following expression to no more than one term. ... ((λx.(x y))(λz.z)) There is a nice introduction to the lambda-calculus: A Tutorial Introduction to
HackerRank Functional Challenges HR F#: Area Under Curves and Volume of Revolving a Curve The next problem, Area Under Curves and Volume of Revolving a Curve, in mathematically advance so I introduce some therms and facts first. Numerical integration is the measuring the area between function and axis, which is done by evaluating function in many points closing to each other and adding together
F# HR F#: Evaluating eˣ The problem Evaluating e^x: The series expansion of eˣ is given by $$1 + x + \frac{x^2} {2!} + \frac{x^3} {3!} + \frac{x^4} {4!} + ...$$ Evaluate eˣ for given values of x by using the above expansion for the first 10 terms. This problem is interesting because it
F# HR F#: Updating List The problem Updating List requires learning how to generate one list from another. Update the values of a list with their absolute values. In many other programming languages the common approach is to update the array items: a[i] = abs(a[i]);, e.g. modify the shared state. The functional
F# HR F#: List Length The problem List Length is interesting because it can be solved using mutable counter but it also can be solved in more functional way. Count the number of elements in an array without using count, size or length operators (or their equivalents). First, let's see on the solution using mutable
F# HR F#: Sum of Odd Elements The problem Sum of Odd Elements: You are given a list. Return the sum of odd elements from the given list. The solusion is basically just an invocation of the List.fold from the standard library: let f arr = arr |> List.fold (fun s v -> if Math.
F# HR F#: Reverse a List The problem Reverse a List encourages to learn List.rev. You are given a list of elements. Reverse the list without using the reverse function. The simplest implementation is not very efficient one but it works good enough to pass the tests: let rev (lst : List<'T>) = let
F# HR F#: Array Of N Elements The problem Array Of N Elements requires to write the function that returns N items. The string serialisation of the data structure should be very specific and similar to [ 1, 2, 3 ]. In the previous solutions I've generated the items using sequences. If sequences was allowed, the solution would be
F# HR F#: Filter Positions in a List The next one is Filter Positions in a List: For a given list with N integers, return a new list removing the elements at odd positions. There are a few methods in the Seq module that looks relevant: iteri and mapi. They both apply the function considering the index of
F# HR F#: Filter Array The next HackerRank functional problem is Filter Array. Filter a given array of integers and output only those values that are less than a specified value X. The idea is to create a filtering function, not using the one from the standard library. With what is already known from solving
F# HR F#: List Replication This is going to be more interesting than[1] previous[2] three[3]. Given a list, repeat each element in the list n amount of times. The first line of the input is a number specifying how many times repeat every element of the list. The list items follow this
