enhance: 数値リテラルに指数表記を追加

src/parser/scanner.ts

@@ -10,6 +10,7 @@ const spaceChars = [' ', '\t'];
 const lineBreakChars = ['\r', '\n'];
 const digit = /^[0-9]$/;
 const wordChar = /^[A-Za-z0-9_]$/;
+const exponentIndicatorPattern = /^[eE]$/;
 
 /**
  * 入力文字列からトークンを読み取るクラス
@@ -436,12 +437,38 @@ export class Scanner implements ITokenStream {
 				throw new AiScriptSyntaxError('digit expected', pos);
 			}
 		}
+
+		let exponentIndicator = '';
+		let exponentSign = '';
+		let exponentAbsolute = '';
+		if (!this.stream.eof && exponentIndicatorPattern.test(this.stream.char as string)) {
+			exponentIndicator = this.stream.char as string;
+			this.stream.next();
+			if (!this.stream.eof && (this.stream.char as string) === '-') {
+				exponentSign = '-';
+				this.stream.next();
+			} else if (!this.stream.eof && (this.stream.char as string) === '+') {
+				exponentSign = '+';
+				this.stream.next();
+			}
+			while (!this.stream.eof && digit.test(this.stream.char)) {
+				exponentAbsolute += this.stream.char;
+				this.stream.next();
+			}
+			if (exponentAbsolute.length === 0) {
+				throw new AiScriptSyntaxError('exponent expected', pos);
+			}
+		}
+
 		let value: string;
 		if (fractional.length > 0) {
 			value = wholeNumber + '.' + fractional;
 		} else {
 			value = wholeNumber;
 		}
+		if (exponentIndicator.length > 0) {
+			value += exponentIndicator + exponentSign + exponentAbsolute;
+		}
 		return TOKEN(TokenKind.NumberLiteral, pos, { hasLeftSpacing, value });
 	}
 

test/literals.ts

@@ -58,6 +58,33 @@ describe('literal', () => {
 		eq(res, NUM(0.5));
 	});
 
+	test.concurrent('number (positive exponent without plus sign)', async () => {
+		const res = await exe(`
+		<: 1.2e3
+		`);
+		eq(res, NUM(1200));
+	});
+
+	test.concurrent('number (positive exponent with plus sign)', async () => {
+		const res = await exe(`
+		<: 1.2e+3
+		`);
+		eq(res, NUM(1200));
+	});
+
+	test.concurrent('number (negative exponent)', async () => {
+		const res = await exe(`
+		<: 1.2e-3
+		`);
+		eq(res, NUM(0.0012));
+	});
+
+	test.concurrent('number (missing exponent)', async () => {
+		assert.rejects(() => exe(`
+		<: 1.2e+
+		`), 'exponent expected');
+	});
+
 	test.concurrent('arr (separated by comma)', async () => {
 		const res = await exe(`
 		<: [1, 2, 3]

unreleased/exponential-notation.md

@@ -0,0 +1 @@
+- 数値リテラルを指数表記で記述できるようになりました。