From ac6b455f4a9be11d322551a927c4330532f9f184 Mon Sep 17 00:00:00 2001
From: Jan Tuomi <jans.tuomi@gmail.com>
Date: Mon, 5 Dec 2022 11:03:32 +0200
Subject: Add record, union concepts

---
 examples/impure-concept.lisp  |  2 +-
 examples/records-concept.lisp | 51 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 1 deletion(-)
 create mode 100644 examples/records-concept.lisp

(limited to 'examples')

diff --git a/examples/impure-concept.lisp b/examples/impure-concept.lisp
index e612339..f769424 100644
--- a/examples/impure-concept.lisp
+++ b/examples/impure-concept.lisp
@@ -3,7 +3,7 @@
 ; Pure functions can only call pure functions.
 ; Impure function names end in an exclamation mark (!) by convention.
 ; The top-level context is impure but has special rules
-;   related to (import!) and (let!).
+;   related to `import!`, `let!`, and other builtins.
 
 ; pure function
 (let! f (\[x] x))
diff --git a/examples/records-concept.lisp b/examples/records-concept.lisp
new file mode 100644
index 0000000..420fa9f
--- /dev/null
+++ b/examples/records-concept.lisp
@@ -0,0 +1,51 @@
+; Records are named tuples with an identifier. `record!` is a builtin function
+; that generates functions for creating, reading and modifying a record.
+; In type system terms, records are intersections.
+
+; `record!` can only be called in the top-level context.
+
+(record! Ns/User
+    name
+    phone-number)
+
+; Generates the following functions:
+
+(let! user
+    (Ns/User/create "John" "010-123-456"))
+    ; user ~> (Ns/User name:"John" phone-number:"010-123-456")
+
+(Ns/User/get-name user) ; => "John"
+(Ns/User/get-phone-number user) ; => "010-123-456"
+
+(Ns/User/set-name "Rick" user)
+    ; => (Ns/User name:"Rick" phone-number:"010-123-456")
+(Ns/User/set-phone-number unit user)
+    ; => (Ns/User name:"Rick" phone-number:<unit>)
+
+
+
+
+; Unions are unions of records with an identifier. `union!` is a builtin function
+; that generates functions for manipulating the records in the union.
+
+; `union!` can only be called in the top-level context.
+
+(union! Ns/Maybe
+    (just value)
+    (nothing))
+
+; Generates the following functions:
+
+(let! m1 (Ns/Maybe/just 10)) ; m1 ~> (Ns/Maybe/Just value:10)
+(let! m2 (Ns/Maybe/nothing)) ; m2 ~> (Ns/Maybe/Nothing)
+
+(Ns/Maybe/Just/get-value m1) ; => 10
+
+
+
+
+; The builtin function `kind` returns the identifier as a string for any record value
+
+(kind m1) ; => "Ns/Maybe/Just"
+(kind m2) ; => "Ns/Maybe/Nothing"
+(kind user) ; => "Ns/User"
-- 
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