♻️ New calculator pending to replace math_expressions

2025-09-13 23:56:17 +08:00
parent 3795b659f6
commit 90a77a2cba
5 changed files with 983 additions and 4 deletions
--- a/lib/parser.dart
+++ b/lib/parser.dart
@@ -0,0 +1,111 @@
+import 'package:simple_math_calc/calculator.dart';
+
+class Parser {
+  final String input;
+  int pos = 0;
+
+  Parser(this.input);
+
+  bool get isEnd => pos >= input.length;
+  String get current => isEnd ? '' : input[pos];
+
+  void eat() => pos++;
+
+  void skipSpaces() {
+    while (!isEnd && input[pos] == ' ') {
+      eat();
+    }
+  }
+
+  Expr parse() => parseAdd();
+
+  Expr parseAdd() {
+    var expr = parseMul();
+    skipSpaces();
+    while (!isEnd && (current == '+' || current == '-')) {
+      var op = current;
+      eat();
+      var right = parseMul();
+      expr = op == '+' ? AddExpr(expr, right) : SubExpr(expr, right);
+      skipSpaces();
+    }
+    return expr;
+  }
+
+  Expr parseMul() {
+    var expr = parseAtom();
+    skipSpaces();
+    while (!isEnd && (current == '*' || current == '/')) {
+      var op = current;
+      eat();
+      var right = parseAtom();
+      if (op == '*') {
+        expr = MulExpr(expr, right);
+      } else {
+        expr = DivExpr(expr, right);
+      }
+      skipSpaces();
+    }
+    return expr;
+  }
+
+  Expr parseAtom() {
+    skipSpaces();
+    if (current == '(') {
+      eat();
+      var expr = parse();
+      if (current != ')') throw Exception("缺少 )");
+      eat();
+      return expr;
+    }
+
+    if (input.startsWith("sqrt", pos)) {
+      pos += 4;
+      if (current != '(') throw Exception("sqrt 缺少 (");
+      eat();
+      var inner = parse();
+      if (current != ')') throw Exception("sqrt 缺少 )");
+      eat();
+      return SqrtExpr(inner);
+    }
+
+    if (input.startsWith("cos", pos)) {
+      pos += 3;
+      if (current != '(') throw Exception("cos 缺少 (");
+      eat();
+      var inner = parse();
+      if (current != ')') throw Exception("cos 缺少 )");
+      eat();
+      return CosExpr(inner);
+    }
+
+    if (input.startsWith("sin", pos)) {
+      pos += 3;
+      if (current != '(') throw Exception("sin 缺少 (");
+      eat();
+      var inner = parse();
+      if (current != ')') throw Exception("sin 缺少 )");
+      eat();
+      return SinExpr(inner);
+    }
+
+    if (input.startsWith("tan", pos)) {
+      pos += 3;
+      if (current != '(') throw Exception("tan 缺少 (");
+      eat();
+      var inner = parse();
+      if (current != ')') throw Exception("tan 缺少 )");
+      eat();
+      return TanExpr(inner);
+    }
+
+    // 解析整数
+    var buf = '';
+    while (!isEnd && RegExp(r'\d').hasMatch(current)) {
+      buf += current;
+      eat();
+    }
+    if (buf.isEmpty) throw Exception("无法解析: $current");
+    return IntExpr(int.parse(buf));
+  }
+}