Some more work on monads

samples/fun/IO.bruijn

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+# read two lines using monadic I/O
+# printf "i love\nmonads\n" | bruijn IO.bruijn
+
+:import std/IO .
+
+main read-line >>= [read-line >>= [return [0 2 1]]]

samples/fun/rng-state.bruijn

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+# MIT License, Copyright (c) 2024 Marvin Borner
+# generates three pseudo-random integers using a state monad
+# printf <seed:number> | bruijn rng-state.bruijn
+
+:import std/Combinator .
+:import std/String .
+:import std/Number .
+:import std/Monad/State .
+
+max (+1000)
+
+rand [[[0 1 1]] rng]
+	rng (+1103515245) ⋅ 0 + (+12345) % max
+
+rand-bool map even? rand
+
+# accumulating bind (reversed)
+triple1 rand >>= (rand >>= (rand >>= [[[[[0 3 [0 3 [0 3 [[0]]]]]]]]]))
+
+:test ((triple1 (+50) [[1]]) =? (+745)) ([[1]])
+
+# normal bind
+triple2 rand >>= [rand >>= [rand >>= [[[0 4 [0 4 [0 4 [[0]]]]]]]]]
+
+:test ((triple2 (+50) [[1]]) =? (+595)) ([[1]])
+
+main string→number → triple2

std/IO.bruijn

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+# MIT License, Copyright (c) 2024 Marvin Borner
+
+:input std/Monad/List .
+
+:import std/Char C
+:import std/Combinator .
+
+# reads a single char monadically
+get-char read
+
+# reads a line monadically
+get-line y [read >>= [(C.eq? 0 '\n') (pure [[0]]) (1 >>= [pure [0 2 1]])]]

std/Monad.bruijn

@@ -1,47 +1,4 @@
-# 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
+# MIT License, Copyright (c) 2024 Marvin Borner
+# just a reference to the list monad (default interface)
 
-:import std/List .
-: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")
-
-# monadifies a list
-lift-m map ⧗ (a → b) → (M a) → (M b)
-
-# monadifies a list with two monadic arguments
-lift-m2 [[[concat ([[4 1 0] <$> 1] <$> 1)]]] ⧗ (a → b → c) → (M a) → (M b) → (M c)
-
-# evaluates monadic actions
-sequence foldr (lift-m2 cons) {}empty ⧗ (List (M a)) → (M (List a))
-
->‣ [sequence ∘∘ 0]
-
-# traverses list based on modifier
-traverse sequence ∘∘ map ⧗ (a → (M b)) → (N a) → (M (N b))
-
-# performs action n times
-replicate-m >replicate ⧗ Number → (M a) → (M (List a))
-
-# maps elements to a monadic action
-map-m >map ⧗ (a → (M b)) → (List a) → (M (List b))
+:input std/Monad/List

std/Monad/List.bruijn

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+# 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/List .
+:import std/Combinator .
+
+read [0] ⧗ a → (M a)
+
+return [[1 : 0]] ⧗ a → (M a)
+
+pure return ⧗ a → (M a)
+
+# monadic bind operator
+bind [[[2 0 1]]] ⧗ (M a) → (a → (M b)) → (M a)
+
+…>>=… bind
+
+: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")
+
+# monadifies a list
+lift-m map ⧗ (a → b) → (M a) → (M b)
+
+# monadifies a list with two monadic arguments
+lift-m2 [[[concat ([[4 1 0] <$> 1] <$> 1)]]] ⧗ (a → b → c) → (M a) → (M b) → (M c)
+
+# evaluates monadic actions
+sequence foldr (lift-m2 cons) {}empty ⧗ (List (M a)) → (M (List a))
+
+>‣ [sequence ∘∘ 0]
+
+# traverses list based on modifier
+traverse sequence ∘∘ map ⧗ (a → (M b)) → (N a) → (M (N b))
+
+# performs action n times
+replicate-m >replicate ⧗ Number → (M a) → (M (List a))
+
+# maps elements to a monadic action
+map-m >map ⧗ (a → (M b)) → (List a) → (M (List b))
+

std/Monad/State.bruijn

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+# MIT License, Copyright (c) 2024 Marvin Borner
+
+:import std/Combinator .
+
+# scala: s0 ⇒ { (s1, a) = run(s0); (s1, f(a)) }
+map [[[1 0 [[[0 2 (5 1)]]]]]] ⧗ (a → b) → (State s a) → (State s b)
+
+# monadic bind/flat-map operator
+# scala: s0 ⇒ { (s1, a) = run(s0); f(a).run(s1) }
+bind [[[2 0 [[3 0 1]]]]] ⧗ (State s a) → (a → (State s b)) → (State s b)
+
+…>>=… bind