From 803231d6202a2686af14bb050cd8e80d5b37a4da Mon Sep 17 00:00:00 2001
From: NunoSempere <nuno.sempere@protonmail.com>
Date: Sun, 4 Sep 2022 17:12:18 +0200
Subject: [PATCH] feat: add a few more simple functions to Danger namespace

---
 .../FunctionRegistry/Library/FR_Danger.res    | 54 ++++++++++++++++++-
 .../src/rescript/Utility/Stdlib.res           |  4 ++
 2 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Danger.res b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Danger.res
index 59ae77cb..e8dbfbbc 100644
--- a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Danger.res
+++ b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_Danger.res
@@ -4,6 +4,22 @@ open FunctionRegistry_Helpers
 let nameSpace = "Danger"
 let requiresNamespace = true
 
+module NumberToNumber = {
+  let make = (name, fn) =>
+    FnDefinition.make(
+      ~name,
+      ~inputs=[FRTypeNumber],
+      ~run=(_, inputs, _, _) => {
+        inputs
+        ->getOrError(0)
+        ->E.R.bind(Prepare.oneNumber)
+        ->E.R2.fmap(fn)
+        ->E.R2.fmap(Wrappers.evNumber)
+      },
+      (),
+    )
+}
+
 module TwoNumbersToNumber = {
   let make = (name, fn) =>
     FnDefinition.make(
@@ -28,18 +44,52 @@ module ThreeNumbersToNumber = {
     )
 }
 
+module Internals = {
+  let factorial = Stdlib.Math.factorial
+  let choose = ((n, k)) => factorial(n) /. (factorial(n -. k) *. factorial(k))
+  let pow = (base, exp) => Js.Math.pow_float(~base, ~exp)
+  let binomial = ((n, k, p)) => choose((n, k)) *. pow(p, k) *. pow(1.0 -. p, n -. k)
+}
+
 let library = [
   Function.make(
     ~name="laplace",
     ~nameSpace,
     ~requiresNamespace,
     ~output=EvtNumber,
-    ~examples=[`laplace(1, 20)`],
+    ~examples=[`Danger.laplace(1, 20)`],
     ~definitions=[
       TwoNumbersToNumber.make("laplace", ((successes, trials)) =>
-        (successes +. 1.0) /. (trials +. 1.0)
+        (successes +. 1.0) /. (trials +. 2.0)
       ),
     ],
     (),
   ),
+  Function.make(
+    ~name="factorial",
+    ~nameSpace,
+    ~requiresNamespace,
+    ~output=EvtNumber,
+    ~examples=[`Danger.factorial(20)`],
+    ~definitions=[NumberToNumber.make("factorial", Internals.factorial)],
+    (),
+  ),
+  Function.make(
+    ~name="choose",
+    ~nameSpace,
+    ~requiresNamespace,
+    ~output=EvtNumber,
+    ~examples=[`Danger.choose(1, 20)`],
+    ~definitions=[TwoNumbersToNumber.make("choose", Internals.choose)],
+    (),
+  ),
+  Function.make(
+    ~name="binomial",
+    ~nameSpace,
+    ~requiresNamespace,
+    ~output=EvtNumber,
+    ~examples=[`Danger.binomial(1, 20, 0.5)`],
+    ~definitions=[ThreeNumbersToNumber.make("binomial", Internals.binomial)],
+    (),
+  ),
 ]
diff --git a/packages/squiggle-lang/src/rescript/Utility/Stdlib.res b/packages/squiggle-lang/src/rescript/Utility/Stdlib.res
index ee43e681..249b93d7 100644
--- a/packages/squiggle-lang/src/rescript/Utility/Stdlib.res
+++ b/packages/squiggle-lang/src/rescript/Utility/Stdlib.res
@@ -47,3 +47,7 @@ module Random = {
   @module external sample: (array<float>, sampleArgs) => array<float> = "@stdlib/random/sample"
   let sample = sample
 }
+
+module Math = {
+  @module external factorial: float => float = "@stdlib/math/base/special/factorial"
+}