Permutations
I started composing a set of APL exercises in response to a query from a new APL enthusiast who attended Morten’s presentation at Functional Conf, Bangalore, October 2014. The first set of exercise are at a low level of difficulty, followed by another set at an intermediate level. One of the intermediate exercises is: Permutations […]
In Praise of Magic Functions: Part II
Part I of this post was concerned with the development speed and execution speed of magic functions and should be read before this post. Benefitting from Future and Past Improvements Looking at the magic function for key in Part I, we see that its performance depends on the following APL primitives, listed with information on […]
In Praise of Magic Functions: Part I
A magic function is an APL-coded (dfn) computation in the C source of the interpreter. For example, some cases of ∧.= are coded as MAGIC(“(≢⍺)(↑∘.=↓)⍺⍳⍺⍪⍉⍵”). The rubric “magic function” includes magic functions and magic operators. Acknowledgments. Magic functions in Dyalog are made possible due to work done by John Scholes and Richard Smith. Development Speed […]
Changes of Heart
Karen Shaw started the ball rolling (hearts afluttering?) by asking Jay Foad to come up with a one-liner for St. Valentine’s Day; he then solicited contributions from the language development group. Nick Nickolov responded with the following, with no explanation other than that there is room for improvement: ⎕io←0 ⋄ (⊢,⌽)’ X'[{(.5×n*2)>+/(⍺-.6×⍵)⍵*2}/¨0↓n-⍳(2×n),n←20] XXXXX XXXXX XXXXXXXXXX […]
Solving the 2014 APL Problem Solving Competition – Cryptography Problem 3
This post is the continuation of the series where we examine some of the problems selected for the 2014 APL Problem Solving Competition. In this post we’ll conclude looking at the cryptography problems from Phase II that we started looking at in a previous blog post and continued in a further blog post. Cryptography Problem […]
Solving the 2014 APL Problem Solving Competition – Cryptography Problem 2
This post is the continuation of the series where we examine some of the problems selected for the 2014 APL Problem Solving Competition. In this post we’ll continue looking at the cryptography problems from Phase II that we started looking at in a previous blog post. Cryptography Problem 2 – Book Cipher Variation Task 1 […]
Solving the 2014 APL Problem Solving Competition – Cryptography Problem 1
This post is a continuation of the series where we examine some of the problems selected for the 2014 APL Problem Solving Competition. I’ll start by looking at the cryptography problems from Phase II. Cryptography Problem 1 – Vigenère Cipher The cipher is described using a large table of letters, but you don’t need to […]
The Diamond Kata
Acknowledgments Morten Kromberg is the other co-author of this text but the blogging software prevents his being listed as such. We are indebted to Jay Foad, Nick Nikolov, John Scholes, and Fiona Smith for comments on successive drafts of the MS. The Problem The diamond kata is a programming exercise used in the agile development, […]
Three-and-a-bit
The most obvious expression for computing π in APL is ○1. But what if you can’t remember how ○ works, or your O key is broken, or you feel like taking the road less travelled? With thanks to Wikipedia’s excellent list of Approximations of π, here are some short sweet APL expressions for three-and-a-bit: 3 ⍝ very short […]
Solving the 2014 APL Problem Solving Competition – it's as easy as 1 1 2 3…
The winners of the 2014 APL Problem Solving Competition were recognized at the Dyalog ’14 user meeting and had a chance to share their competition experiences. Emil Bremer Orloff won the student competition and received $2500 USD and an expenses-paid trip to Dyalog ’14, while Iryna Pashenkovska took first place among the non-student entries and received a complimentary […]
