From c944841dc68252ae3da9d8094ad691bad4fcb027 Mon Sep 17 00:00:00 2001
From: Sergiu Ivanov <sivanov@colimite.fr>
Date: Wed, 9 Aug 2023 23:15:33 +0200
Subject: [PATCH] Add NonemptyListof.

---
 scribblings/utils.scrbl | 6 ++++++
 utils.rkt               | 4 +++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/scribblings/utils.scrbl b/scribblings/utils.scrbl
index 6326dfc..b177ec9 100644
--- a/scribblings/utils.scrbl
+++ b/scribblings/utils.scrbl
@@ -45,6 +45,12 @@ the variables.
 
 }
 
+@defform[(NonemptyListof a)]{
+
+A @racket[(Listof a)] which contains at least one element.
+
+}
+
 @section{Type utilities}
 
 Typed Racket's @racket[cast] should only be used as a last resort, because it
diff --git a/utils.rkt b/utils.rkt
index a9ca75d..4f1a7ae 100644
--- a/utils.rkt
+++ b/utils.rkt
@@ -4,7 +4,7 @@
          (for-syntax syntax/parse racket/syntax racket/list))
 
 (provide
- Variable VariableMapping GeneralPair
+ Variable VariableMapping GeneralPair NonemptyListof
 
  assert-type for/first/typed for*/first/typed define/abstract/error
  relax-arg-type/any
@@ -28,6 +28,8 @@
 (define-type Variable Symbol)
 (define-type (VariableMapping A) (Immutable-HashTable Variable A))
 
+(define-type (NonemptyListof a) (Pairof a (Listof a)))
+
 (define-syntax-parse-rule (assert-type e:expr type:expr)
   (assert e (make-predicate type)))