From ca808bc09373f123514bf865a4518bebac3bbbc3 Mon Sep 17 00:00:00 2001
From: Marvin Borner
Date: Sun, 5 Mar 2023 14:44:40 +0100
Subject: Monadic list/io interface

---
 std/Monad.bruijn | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 std/Monad.bruijn

(limited to 'std/Monad.bruijn')

diff --git a/std/Monad.bruijn b/std/Monad.bruijn
new file mode 100644
index 0000000..e015efa
--- /dev/null
+++ b/std/Monad.bruijn
@@ -0,0 +1,27 @@
+# MIT License, Copyright (c) 2023 Marvin Borner
+# monadic interface for anything based on lists (e.g. IO, strings)
+# afaik originally proposed by John Tromp and inspired by Haskell
+
+:import std/Pair .
+:import std/Combinator .
+
+read [0] ⧗ a → (M a)
+
+return [[1 : 0]] ⧗ a → (M a)
+
+pure return ⧗ a → (M a)
+
+# monadic bind operator
+…>>=… [[[2 0 1]]] ⧗ (M a) → (a → (M b)) → (M a)
+
+:test ((read >>= return) "woa") ("woa")
+
+# monadic reverse bind operator
+…=<<… \…>>=… ⧗ (a → (M b)) → (M a) → (M b)
+
+:test ((return =<< read) "woa") ("woa")
+
+# monadic compose operator
+…>>… [[1 >>= [1]]] ⧗ (M a) → (M b) → (M b)
+
+:test ((read >> (return 'a')) "hah") ("aah")
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