enhance: 数値リテラルの整数部分または小数部分の0を省略できるように

src/parser/scanner.ts

@@ -209,6 +209,10 @@ export class Scanner implements ITokenStream {
 				}
 				case '.': {
 					this.stream.next();
+					if (!this.stream.eof && digit.test(this.stream.char as string)) {
+						const digitToken = this.tryReadDigits(hasLeftSpacing, pos, true);
+						if (digitToken) return digitToken;
+					}
 					return TOKEN(TokenKind.Dot, pos, { hasLeftSpacing });
 				}
 				case '/': {
@@ -321,7 +325,7 @@ export class Scanner implements ITokenStream {
 					return TOKEN(TokenKind.CloseBrace, pos, { hasLeftSpacing });
 				}
 				default: {
-					const digitToken = this.tryReadDigits(hasLeftSpacing);
+					const digitToken = this.tryReadDigits(hasLeftSpacing, pos, false);
 					if (digitToken) return digitToken;
 
 					const wordToken = this.tryReadWord(hasLeftSpacing);
@@ -484,26 +488,33 @@ export class Scanner implements ITokenStream {
 		return `u${code}`;
 	}
 
-	private tryReadDigits(hasLeftSpacing: boolean): Token | undefined {
+	private tryReadDigits(
+		hasLeftSpacing: boolean,
+		pos: { line: number, column: number },
+		hasLeadingDot: boolean,
+	): Token | undefined {
 		let wholeNumber = '';
 		let fractional = '';
 
-		const pos = this.stream.getPos();
-
-		while (!this.stream.eof && digit.test(this.stream.char)) {
-			wholeNumber += this.stream.char;
-			this.stream.next();
-		}
-		if (wholeNumber.length === 0) {
-			return;
+		if (!hasLeadingDot) {
+			while (!this.stream.eof && digit.test(this.stream.char)) {
+				wholeNumber += this.stream.char;
+				this.stream.next();
+			}
+			if (wholeNumber.length === 0) {
+				return;
+			}
 		}
-		if (!this.stream.eof && this.stream.char === '.') {
-			this.stream.next();
+		const decimalPoint = this.tryReadDecimalPoint(hasLeadingDot);
+		if (decimalPoint) {
+			if (this.stream.char === '.') {
+				throw new AiScriptSyntaxError('dot cannot follow a decimal point', this.stream.getPos());
+			}
 			while (!this.stream.eof as boolean && digit.test(this.stream.char as string)) {
 				fractional += this.stream.char;
 				this.stream.next();
 			}
-			if (fractional.length === 0) {
+			if (wholeNumber.length === 0 && fractional.length === 0) {
 				throw new AiScriptSyntaxError('digit expected', pos);
 			}
 		}
@@ -542,6 +553,17 @@ export class Scanner implements ITokenStream {
 		return TOKEN(TokenKind.NumberLiteral, pos, { hasLeftSpacing, value });
 	}
 
+	private tryReadDecimalPoint(hasLeadingDot: boolean): boolean {
+		if (hasLeadingDot) {
+			return true;
+		}
+		if (!this.stream.eof && this.stream.char === '.') {
+			this.stream.next();
+			return true;
+		}
+		return false;
+	}
+
 	private readStringLiteral(hasLeftSpacing: boolean): Token {
 		let value = '';
 		const literalMark = this.stream.char;

test/literals.ts

@@ -85,6 +85,62 @@ describe('literal', () => {
 		`), 'exponent expected');
 	});
 
+	test.concurrent('number (Float with integer zero omitted)', async () => {
+		const res = await exe(`
+		<: .5
+		`);
+		eq(res, NUM(0.5));
+	});
+
+	test.concurrent('number (Float with decimal zero omitted)', async () => {
+		const res = await exe(`
+		<: 5.
+		`);
+		eq(res, NUM(5));
+	});
+
+	test.concurrent('number (integer zero omitted, positive exponent without plus sign)', async () => {
+		const res = await exe(`
+		<: .5e3
+		`);
+		eq(res, NUM(500));
+	});
+
+	test.concurrent('number (integer zero omitted, positive exponent with plus sign)', async () => {
+		const res = await exe(`
+		<: .5e+3
+		`);
+		eq(res, NUM(500));
+	});
+
+	test.concurrent('number (integer zero omitted, negative exponent)', async () => {
+		const res = await exe(`
+		<: .5e-3
+		`);
+		eq(res, NUM(0.0005));
+	});
+
+	test.concurrent('number (decimal zero omitted, positive exponent without plus sign)', async () => {
+		const res = await exe(`
+		<: 5.e3
+		`);
+		eq(res, NUM(5000));
+	});
+
+	test.concurrent('number (decimal zero omitted, positive exponent with plus sign)', async () => {
+		const res = await exe(`
+		<: 5.e+3
+		`);
+		eq(res, NUM(5000));
+	});
+
+	test.concurrent('number (decimal zero omitted, negative exponent)', async () => {
+		const res = await exe(`
+		<: 5.e-3
+		`);
+		eq(res, NUM(0.005));
+	});
+
 	test.concurrent('arr (separated by comma)', async () => {
 		const res = await exe(`
 		<: [1, 2, 3]

test/syntax.ts

@@ -1,8 +1,8 @@
 import * as assert from 'assert';
-import { describe, test } from 'vitest';
+import { describe, expect, test } from 'vitest';
 import { utils } from '../src';
 import { NUM, STR, NULL, ARR, OBJ, BOOL, TRUE, FALSE, ERROR ,FN_NATIVE } from '../src/interpreter/value';
-import { AiScriptRuntimeError, AiScriptUnexpectedEOFError } from '../src/error';
+import { AiScriptRuntimeError, AiScriptSyntaxError, AiScriptUnexpectedEOFError } from '../src/error';
 import { exe, getMeta, eq } from './testutils';
 
 /*
@@ -1485,6 +1485,18 @@ describe('Infix expression', () => {
 			NUM(3)
 		);
 	});
+
+	test.concurrent('dot cannot follow a decimal point', async () => {
+		await expect(() => exe(`
+		<: 1..to_str()
+		`)).rejects.toThrow(AiScriptSyntaxError);
+	});
+
+	test.concurrent('dot following parenthesis after decimal point', async () => {
+		eq(await exe(`
+		<: (1.).to_str()
+		`), STR('1'));
+	});
 });
 
 describe('if', () => {

unreleased/zero-part-ommitable-decimal-literal.md

@@ -0,0 +1,3 @@
+- 数値リテラルの整数部分または小数部分の0を省略できるようになりました。
+	- 整数でない数値リテラルは、整数部分が0の場合、0を省略して記述できるようになりました。
+	- 整数の数値リテラルは、小数部分の0を省略して記述できるようになりました。