Add two-fer exercise

config.json

@@ -15,6 +15,16 @@
         "text_formatting"
       ]
     },
+    {
+      "slug": "two-fer",
+      "uuid": "34f6e27c-9f14-4311-bc71-1f24958795a2",
+      "core": true,
+      "unlocked_by": null,
+      "difficulty": 1,
+      "topics": [
+        "strings"
+      ]
+    },
     {
       "slug": "leap",
       "uuid": "4be11d9f-db6a-4edd-af35-7d33d2dc9c0f",
@@ -368,8 +378,8 @@
       "unlocked_by": null,
       "difficulty": 1,
       "topics": [
-        "strings",
-        "filtering"
+        "filtering",
+        "strings"
       ]
     }
   ]

exercises/acronym/README.md

@@ -8,7 +8,7 @@ Help generate some jargon by writing a program that converts a long name
 like Portable Network Graphics to its acronym (PNG).
 
 ## Installation
-See [this guide](https://github.com/exercism/xr/blob/master/docs/INSTALLATION.md) for instructions on how to setup your local R environment.
+See [this guide](https://exercism.io/tracks/r/installation) for instructions on how to setup your local R environment.
 
 ## How to implement your solution
 In each problem folder, there is a file named `<exercise_name>.R` containing a function that returns a `NULL` value. Place your implementation inside the body of the function.

exercises/bob/README.md

@@ -13,8 +13,6 @@ anything.
 
 He answers 'Whatever.' to anything else.
 
-Bob's conversational partner is a purist when it comes to written communication and always follows normal rules regarding sentence punctuation in English.
-
 ## Installation
 See [this guide](https://exercism.io/tracks/r/installation) for instructions on how to setup your local R environment.
 

exercises/crypto-square/README.md

@@ -12,15 +12,11 @@ regarded as forming a rectangle when printed with intervening newlines.
 
 For example, the sentence
 
-```text
-"If man was meant to stay on the ground, god would have given us roots."
-```
+> If man was meant to stay on the ground, god would have given us roots.
 
 is normalized to:
 
-```text
-"ifmanwasmeanttostayonthegroundgodwouldhavegivenusroots"
-```
+> ifmanwasmeanttostayonthegroundgodwouldhavegivenusroots
 
 The plaintext should be organized in to a rectangle.  The size of the
 rectangle (`r x c`) should be decided by the length of the message,
@@ -31,13 +27,13 @@ Our normalized text is 54 characters long, dictating a rectangle with
 `c = 8` and `r = 7`:
 
 ```text
-"ifmanwas"
-"meanttos"
-"tayonthe"
-"groundgo"
-"dwouldha"
-"vegivenu"
-"sroots  "
+ifmanwas
+meanttos
+tayonthe
+groundgo
+dwouldha
+vegivenu
+sroots
 ```
 
 The coded message is obtained by reading down the columns going left to
@@ -46,30 +42,31 @@ right.
 The message above is coded as:
 
 ```text
-"imtgdvsfearwermayoogoanouuiontnnlvtwttddesaohghnsseoau"
+imtgdvsfearwermayoogoanouuiontnnlvtwttddesaohghnsseoau
 ```
 
-Output the encoded text in chunks that fill perfect rectangles `(r X c)`,
-with `c` chunks of `r` length, separated by spaces. For phrases that are
-`n` characters short of the perfect rectangle, pad each of the last `n`
-chunks with a single trailing space.
+Output the encoded text in chunks.  Phrases that fill perfect rectangles
+`(r X c)` should be output `c` chunks of `r` length, separated by spaces.
+Phrases that do not fill perfect rectangles will have `n` empty spaces.
+Those spaces should be distributed evenly, added to the end of the last
+`n` chunks.
 
 ```text
-"imtgdvs fearwer mayoogo anouuio ntnnlvt wttddes aohghn  sseoau "
+imtgdvs fearwer mayoogo anouuio ntnnlvt wttddes aohghn  sseoau 
 ```
 
 Notice that were we to stack these, we could visually decode the
 cyphertext back in to the original message:
 
 ```text
-"imtgdvs"
-"fearwer"
-"mayoogo"
-"anouuio"
-"ntnnlvt"
-"wttddes"
-"aohghn "
-"sseoau "
+imtgdvs
+fearwer
+mayoogo
+anouuio
+ntnnlvt
+wttddes
+aohghn
+sseoau
 ```
 
 ## Installation

exercises/hamming/README.md

@@ -31,10 +31,9 @@ The Hamming distance between these two DNA strands is 7.
 
 # Implementation notes
 
-The Hamming distance is only defined for sequences of equal length, so
-an attempt to calculate it between sequences of different lengths should
-not work. The general handling of this situation (e.g., raising an
-exception vs returning a special value) may differ between languages.
+The Hamming distance is only defined for sequences of equal length. This means
+that based on the definition, each language could deal with getting sequences
+of equal length differently.
 
 ## Installation
 See [this guide](https://exercism.io/tracks/r/installation) for instructions on how to setup your local R environment.

exercises/sieve/README.md

@@ -5,8 +5,8 @@ number.
 
 The Sieve of Eratosthenes is a simple, ancient algorithm for finding all
 prime numbers up to any given limit. It does so by iteratively marking as
-composite (i.e. not prime) the multiples of each prime, starting with the
-multiples of 2. It does not use any division or remainder operation.
+composite (i.e. not prime) the multiples of each prime,
+starting with the multiples of 2.
 
 Create your range, starting at two and continuing up to and including the given limit. (i.e. [2, limit])
 
@@ -25,9 +25,7 @@ https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
 
 Notice that this is a very specific algorithm, and the tests don't check
 that you've implemented the algorithm, only that you've come up with the
-correct list of primes. A good first test is to check that you do not use
-division or remainder operations (div, /, mod or % depending on the
-language).
+correct list of primes.
 
 ## Installation
 See [this guide](https://exercism.io/tracks/r/installation) for instructions on how to setup your local R environment.

exercises/two-fer/README.md

@@ -0,0 +1,29 @@
+# Two Fer
+
+`Two-fer` or `2-fer` is short for two for one. One for you and one for me.
+
+```text
+"One for X, one for me."
+```
+
+When X is a name or "you".
+
+If the given name is "Alice", the result should be "One for Alice, one for me."
+If no name is given, the result should be "One for you, one for me."
+
+
+## Installation
+See [this guide](https://exercism.io/tracks/r/installation) for instructions on how to setup your local R environment.
+
+## How to implement your solution
+In each problem folder, there is a file named `<exercise_name>.R` containing a function that returns a `NULL` value. Place your implementation inside the body of the function.
+
+## How to run tests
+Inside of RStudio, simply execute the `test_<exercise_name>.R` script. This can be conveniently done with [testthat's `auto_test` function](https://www.rdocumentation.org/packages/testthat/topics/auto_test). Because exercism code and tests are in the same folder, use this same path for both  `code_path` and `test_path` parameters. On the command-line, you can also run `Rscript test_<exercise_name>.R`.
+
+## Source
+
+[https://en.wikipedia.org/wiki/Two-fer](https://en.wikipedia.org/wiki/Two-fer)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

exercises/two-fer/example.R

@@ -0,0 +1,3 @@
+two_fer <- function(input = "you") {
+  sprintf("One for %s, one for me.", input)
+}

exercises/two-fer/test_two-fer.R

@@ -0,0 +1,18 @@
+source("./two-fer.R")
+library(testthat)
+
+context("two-fer")
+
+test_that("Abbreviate a phrase", {
+  expect_equal(two_fer(), "One for you, one for me.")
+})
+
+test_that("Abbreviate a phrase", {
+  expect_equal(two_fer("Alice"), "One for Alice, one for me.")
+})
+
+test_that("Abbreviate a phrase", {
+  expect_equal(two_fer("Bob"), "One for Bob, one for me.")
+})
+
+message("All tests passed for exercise: two-fer")

exercises/two-fer/two-fer.R

@@ -0,0 +1,3 @@
+two_fer <- function(input) {
+
+}