From aff5cbd546f68d6c400cdf042d20d295a695741e Mon Sep 17 00:00:00 2001
From: colinleach <colin.leach@comcast.net>
Date: Sat, 8 Jul 2023 15:18:14 -0700
Subject: [PATCH 1/2] set-operations concept

---
 concepts/set-operations/.meta/config.json |  5 +++
 concepts/set-operations/about.md          | 39 +++++++++++++++++++++++
 concepts/set-operations/introduction.md   | 13 ++++++++
 concepts/set-operations/links.json        |  6 ++++
 config.json                               |  5 +++
 5 files changed, 68 insertions(+)
 create mode 100644 concepts/set-operations/.meta/config.json
 create mode 100644 concepts/set-operations/about.md
 create mode 100644 concepts/set-operations/introduction.md
 create mode 100644 concepts/set-operations/links.json

diff --git a/concepts/set-operations/.meta/config.json b/concepts/set-operations/.meta/config.json
new file mode 100644
index 00000000..15b9f30e
--- /dev/null
+++ b/concepts/set-operations/.meta/config.json
@@ -0,0 +1,5 @@
+{
+  "authors": ["colinleach"],
+  "contributors": [],
+  "blurb": "Core R provides several functions that perform set-like operations on vectors."
+}
\ No newline at end of file
diff --git a/concepts/set-operations/about.md b/concepts/set-operations/about.md
new file mode 100644
index 00000000..8c37efa9
--- /dev/null
+++ b/concepts/set-operations/about.md
@@ -0,0 +1,39 @@
+# Introduction
+
+R has no separate Set datatype, instead using a variety of functions to perform similar operations on vectors.
+
+We have already seen `%in%` to test for set membership:
+
+```R
+2 %in% 1:10 # TRUE
+12 %in% 1:10 # FALSE
+```
+
+Relevant functions include `unique` to remove duplicates, plus `union()`, `intersect()` and `setdiff()` to operate on pairs of sets.
+
+```R
+> set_1 <- c("a", "b", "c", "b", "a")
+> unique(set_1) # deduplicate
+[1] "a" "b" "c"
+
+> set_2 <- c('a', "c", "d")
+> union(set_1, set_2) # values in either set
+[1] "a" "b" "c" "d"
+
+> intersect(set_1, set_2) # values in both sets
+[1] "a" "c"
+
+> setdiff(set_1, set_2) # values in set_1 but not set_2
+[1] "b"
+
+> setdiff(set_2, set_1)
+[1] "d"
+```
+
+## The `hashtable` package
+
+The vector operations described above are part of core R.
+These are useful for small problems but become slow for large sets.
+
+The `hashtable` package provides implementations of `hashmap` and `hashset` which scale better.
+Like most external packages, this is not available within Exercism, but is worth investigating for real-world problems.
diff --git a/concepts/set-operations/introduction.md b/concepts/set-operations/introduction.md
new file mode 100644
index 00000000..6b59684a
--- /dev/null
+++ b/concepts/set-operations/introduction.md
@@ -0,0 +1,13 @@
+# Introduction
+
+R has no separate Set datatype, instead using a variety of functions to perform similar operations on vectors.
+
+We have already seen `%in%` to test for set membership:
+
+```R
+2 %in% 1:10 # TRUE
+12 %in% 1:10 # FALSE
+```
+
+Relevant functions include `unique` (to remove duplicates), `union()`, `intersect()` and `setdiff()` to operate on pairs of sets.
+Details are available online.
diff --git a/concepts/set-operations/links.json b/concepts/set-operations/links.json
new file mode 100644
index 00000000..88ed67cd
--- /dev/null
+++ b/concepts/set-operations/links.json
@@ -0,0 +1,6 @@
+[
+    {
+      "url": "https://search.r-project.org/CRAN/refmans/generics/html/setops.html",
+      "description": "Set Operations"
+    }
+  ]
\ No newline at end of file
diff --git a/config.json b/config.json
index 312e341d..9bd21030 100644
--- a/config.json
+++ b/config.json
@@ -540,6 +540,11 @@
       "uuid": "d75c1a77-9733-45b0-ae21-2b4f0f313ef4",
       "slug": "basics",
       "name": "Basics"
+    },
+    {
+      "uuid": "85db3d8c-dfec-424c-9682-caa8611db8f8",
+      "slug": "set-operations",
+      "name": "Set Operations"
     }
   ],
   "key_features": [

From 3a957792e77e454e1ac0564a3e924260c5294dd4 Mon Sep 17 00:00:00 2001
From: colinleach <colin.leach@comcast.net>
Date: Sat, 8 Jul 2023 15:37:50 -0700
Subject: [PATCH 2/2] small fixes for setoperations

---
 concepts/set-operations/.meta/config.json |  2 +-
 concepts/set-operations/links.json        | 10 +++++-----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/concepts/set-operations/.meta/config.json b/concepts/set-operations/.meta/config.json
index 15b9f30e..d9226c05 100644
--- a/concepts/set-operations/.meta/config.json
+++ b/concepts/set-operations/.meta/config.json
@@ -2,4 +2,4 @@
   "authors": ["colinleach"],
   "contributors": [],
   "blurb": "Core R provides several functions that perform set-like operations on vectors."
-}
\ No newline at end of file
+}
diff --git a/concepts/set-operations/links.json b/concepts/set-operations/links.json
index 88ed67cd..24e5d70f 100644
--- a/concepts/set-operations/links.json
+++ b/concepts/set-operations/links.json
@@ -1,6 +1,6 @@
 [
-    {
-      "url": "https://search.r-project.org/CRAN/refmans/generics/html/setops.html",
-      "description": "Set Operations"
-    }
-  ]
\ No newline at end of file
+  {
+    "url": "https://search.r-project.org/CRAN/refmans/generics/html/setops.html",
+    "description": "Set Operations"
+  }
+]