X-Git-Url: https://git.ladys.computer/Pisces/blobdiff_plain/d78461254503ec9dab25d0a7518538e9149618e2..6e6d4e3261c1c943fe44fa9e381bcf8bf1441fd6:/numeric.js

diff --git a/numeric.js b/numeric.js
index f16308d..4a066f7 100644
--- a/numeric.js
+++ b/numeric.js
@@ -7,6 +7,14 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at <https://mozilla.org/MPL/2.0/>.
 
+import { call } from "./function.js";
+import {
+  stringCatenate,
+  stringPadEnd,
+  stringRepeat,
+  substring,
+  toString,
+} from "./string.js";
 import { sameValue, toPrimitive } from "./value.js";
 
 export const {
@@ -584,6 +592,93 @@ export const { toBigInt } = (() => {
   return { toBigInt: ($) => makeBigInt($) };
 })();
 
+export const {
+  /**
+   * Returns the result of converting the provided value to an
+   * exponential notation string.
+   *
+   * If a second argument is provided, it gives the number of
+   * fractional digits to use in the mantissa. Otherwise, the smallest
+   * number which does not result in a reduction in precision is used.
+   *
+   * ※ This method is safe to use with big·ints.
+   */
+  toExponentialNotation,
+
+  /**
+   * Returns the result of converting the provided value to a fixed
+   * decimal notation string with the provided number of fractional
+   * digits.
+   *
+   * ※ This method is safe to use with big·ints.
+   */
+  toFixedDecimalNotation,
+} = (() => {
+  const {
+    toExponential: numberToExponential,
+    toFixed: numberToFixed,
+  } = Number.prototype;
+  const { toString: bigintToString } = BigInt.prototype;
+  return {
+    toExponentialNotation: ($, fractionDigits) => {
+      const n = toNumeric($);
+      const f = toIntegralNumberOrInfinity(fractionDigits);
+      if (!isFiniteNumber(f) || f < 0 || f > 100) {
+        throw new RangeError(
+          `Piscēs: The number of fractional digits must be a finite number between 0 and 100 inclusive; got: ${f}.`,
+        );
+      } else {
+        if (typeof n === "number") {
+          return call(
+            numberToExponential,
+            n,
+            [fractionDigits === undefined ? fractionDigits : f],
+          );
+        } else {
+          const digits = call(bigintToString, n, [10]);
+          const { length } = digits;
+          if (fractionDigits === undefined) {
+            return length === 1
+              ? `${digits[0]}e+0`
+              : `${digits[0]}.${substring(digits, 1)}e+${length - 1}`;
+          } else if (f === 0) {
+            return `${digits[0]}e+0`;
+          } else {
+            const fractionalPart = toString(
+              round(
+                +stringCatenate(
+                  stringPadEnd(substring(digits, 1, f + 1), f, "0"),
+                  ".",
+                  digits[f + 1] || "0",
+                ),
+              ),
+            );
+            return `${digits[0]}.${fractionalPart}e+${length - 1}`;
+          }
+        }
+      }
+    },
+    toFixedDecimalNotation: ($, fractionDigits) => {
+      const f = toIntegralNumberOrInfinity(fractionDigits);
+      if (!isFiniteNumber(f) || f < 0 || f > 100) {
+        throw new RangeError(
+          `Piscēs: The number of fractional digits must be a finite number between 0 and 100 inclusive; got: ${f}.`,
+        );
+      } else {
+        const n = toNumeric($);
+        if (typeof n === "number") {
+          return call(numberToFixed, n, [f]);
+        } else {
+          const digits = call(bigintToString, n, [10]);
+          return f === 0
+            ? digits
+            : `${digits}.${stringRepeat("0", f)}`;
+        }
+      }
+    },
+  };
+})();
+
 export const {
   /**
    * Returns the result of converting the provided value to fit within
@@ -687,7 +782,7 @@ export const toIntegralNumberOrInfinity = ($) => {
 /**
  * Returns the result of converting the provided value to a number.
  *
- * ※ This method is safe to use with big·ints.
+ * ※ This function is safe to use with big·ints.
  *
  * ※ This is effectively a nonconstructible version of the Number
  * constructor.