From 5805bfeee4c9c2f713042b34e41821be153cac7c Mon Sep 17 00:00:00 2001
From: Xie Yuheng <xyheme@gmail.com>
Date: Mon, 24 Jun 2024 20:53:29 +0800
Subject: [PATCH] `utils/coercing` -- improve generic functions

---
 TODO.md                    | 31 +++++++++++++++----------------
 src/generics/arithmetic.ts | 10 ++++------
 src/interval/Interval.ts   |  5 +++++
 src/utils/coercing.ts      |  6 ++++++
 4 files changed, 30 insertions(+), 22 deletions(-)
 create mode 100644 src/utils/coercing.ts

diff --git a/TODO.md b/TODO.md
index 9b0aded..c7faed1 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,33 +1,32 @@
-improve interface for `put` -- second argument should be list of optional promises
-
-`applyAfter` (`coercing`)
+# propagator 支持 dependencies for provenance
 
-> propagator 支持 dependencies for provenance
->
 > - https://github.com/cicada-lang/propagator/issues/2
-
-测试反向运算的 provenance
-
-test about "a justified-intervals anomaly"
+>   `coercing(toInterval, f)`
+>   `coercing(toSupported, f)`
+>   测试反向运算的 provenance
+>   test about "a justified-intervals anomaly"
 
 - 即 supports 的集合可能与 supported value put 进来的顺序有关
 
+# later
+
+improve interface for `put` -- second argument should be list of optional promises
 `utils/Set` -- `setIntersection` & `setDifference` -- 为了完备
 
-> propagator 支持 dependencies for alternate worldviews
->
+# propagator 支持 dependencies for alternate worldviews
+
 > - https://github.com/cicada-lang/propagator/issues/3
 
-> propagator 支持 dependencies for implicit search
->
+# propagator 支持 dependencies for implicit search
+
 > - https://github.com/cicada-lang/propagator/issues/4
 
-> 完成 "The Art" 中的 Heron 例子
->
+# 完成 "The Art" 中的 Heron 例子
+
 > - 需要设计 lattice 来逼近结果
 >   - 一个叫 近似值 的数据类型，并且为 generic 函数实现相关的 handles
 
-> interval 支持完整的 arithmetic，包括正数与负数
+# interval 支持完整的 arithmetic，包括正数与负数
 
 `interval/` -- arithmetic 支持负数
 
diff --git a/src/generics/arithmetic.ts b/src/generics/arithmetic.ts
index d552fc7..ad58e1d 100644
--- a/src/generics/arithmetic.ts
+++ b/src/generics/arithmetic.ts
@@ -6,18 +6,16 @@ import {
   intervalMul,
   intervalSub,
   isInterval,
+  toInterval,
 } from "../interval/index.js"
+import { coercing } from "../utils/coercing.js"
 import { isNumber } from "../utils/isNumber.js"
 
 export const add = defineGeneric()
 defineHandler(add, [isNumber, isNumber], (x, y) => x + y)
 defineHandler(add, [isInterval, isInterval], intervalAdd)
-defineHandler(add, [isInterval, isNumber], (x, y) =>
-  intervalAdd(x, exactInterval(y)),
-)
-defineHandler(add, [isNumber, isInterval], (x, y) =>
-  intervalAdd(exactInterval(x), y),
-)
+defineHandler(add, [isInterval, isNumber], coercing(toInterval, intervalAdd))
+defineHandler(add, [isNumber, isInterval], coercing(toInterval, intervalAdd))
 
 export const sub = defineGeneric()
 defineHandler(sub, [isNumber, isNumber], (x, y) => x - y)
diff --git a/src/interval/Interval.ts b/src/interval/Interval.ts
index 11dc65a..73fe143 100644
--- a/src/interval/Interval.ts
+++ b/src/interval/Interval.ts
@@ -21,3 +21,8 @@ export function exactInterval(x: number): Interval {
 export function isInterval(x: any): x is Interval {
   return isNonNullObject(x) && x["@type"] === "Interval"
 }
+
+export function toInterval(x: number | Interval): Interval {
+  if (isInterval(x)) return x
+  return exactInterval(x)
+}
diff --git a/src/utils/coercing.ts b/src/utils/coercing.ts
new file mode 100644
index 0000000..bbc454a
--- /dev/null
+++ b/src/utils/coercing.ts
@@ -0,0 +1,6 @@
+export function coercing<A, B, C>(
+  to: (x: A) => B,
+  fn: (...args: Array<B>) => C,
+): (...args: Array<A>) => C {
+  return (...args) => fn(...args.map(to))
+}