feat(positive_number): add validator for positive number

validators/number/positive_number.ts

@@ -0,0 +1,16 @@
+// Copyright 2023-latest Tomoki Miyauchi. All rights reserved. MIT license.
+// This module is browser compatible.
+
+import { shouldBeBut } from "../utils.ts";
+import { display, ScalarValidator } from "../../utils.ts";
+import { isPositiveNumber } from "../../deps.ts";
+
+@display("positive number")
+export class PositiveNumberValidator extends ScalarValidator<number> {
+  constructor() {
+    super();
+    super.expect(shouldBeBut);
+  }
+
+  is = isPositiveNumber;
+}

validators/utils.ts

@@ -0,0 +1,20 @@
+// Copyright 2023-latest Tomoki Miyauchi. All rights reserved. MIT license.
+// This module is browser compatible.
+
+import { format } from "../utils.ts";
+import error from "./error.json" assert { type: "json" };
+import type { Display } from "../types.ts";
+
+export function displayOr(input: readonly unknown[]): string {
+  const head = input.slice(0, -1);
+  const last = input.slice(-1)[0];
+
+  return head.join(", ") + " or " + last;
+}
+
+export function shouldBeBut(
+  this: Display,
+  { input }: { input: unknown },
+): string {
+  return format(error.should_be_but, this, input);
+}