使用ANTLR的嵌套布尔表达式解析器

我只是将所有表达式包装成一条

expression

comparator

binary

comparator

OR

AND

grammar SimpleBoolean;parse : expression EOF ;expression : LPAREN expression RPAREN #parenexpression | NOT expression#notexpression | left=expression op=comparator right=expression #comparatorexpression | left=expression op=binary right=expression     #binaryexpression | bool          #boolexpression | IDENTIFIER    #identifierexpression | DECIMAL       #decimalexpression ;comparator : GT | GE | LT | LE | EQ ;binary : AND | OR ;bool : TRUE | FALSE ;AND        : 'AND' ;OR         : 'OR' ;NOT        : 'NOT';TRUE       : 'TRUE' ;FALSE      : 'FALSE' ;GT         : '>' ;GE         : '>=' ;LT         : '<' ;LE         : '<=' ;EQ         : '=' ;LPAREN     : '(' ;RPAREN     : ')' ;DECIMAL    : '-'? [0-9]+ ( '.' [0-9]+ )? ;IDENTIFIER : [a-zA-Z_] [a-zA-Z_0-9]* ;WS         : [ rtu000Cn]+ -> skip;

要测试上面的语法，请使用以下快速测试类：

public class Main {  public static void main(String[] args) throws Exception {    Map<String, Object> variables = new HashMap<String, Object>() {{      put("A", true);      put("a", true);      put("B", false);      put("b", false);      put("C", 42.0);      put("c", 42.0);      put("D", -999.0);      put("d", -1999.0);      put("E", 42.001);      put("e", 142.001);      put("F", 42.001);      put("f", 42.001);      put("G", -1.0);      put("g", -1.0);    }};    String[] expressions = {        "1 > 2",        "1 >= 1.0",        "TRUE = FALSE",        "FALSE = FALSE",        "A OR B",        "B",        "A = B",        "c = C",        "E > D",        "B OR (c = B OR (A = A AND c = C AND E > D))",        "(A = a OR B = b OR C = c AND ((D = d AND E = e) OR (F = f AND G = g)))"    };    for (String expression : expressions) {      SimpleBooleanLexer lexer = new SimpleBooleanLexer(new ANTLRInputStream(expression));      SimpleBooleanParser parser = new SimpleBooleanParser(new CommonTokenStream(lexer));      Object result = new evalVisitor(variables).visit(parser.parse());      System.out.printf("%-70s -> %sn", expression, result);    }  }}class evalVisitor extends SimpleBooleanbaseVisitor<Object> {  private final Map<String, Object> variables;  public evalVisitor(Map<String, Object> variables) {    this.variables = variables;  }  @Override  public Object visitParse(SimpleBooleanParser.ParseContext ctx) {    return super.visit(ctx.expression());  }  @Override  public Object visitDecimalexpression(SimpleBooleanParser.DecimalexpressionContext ctx) {    return Double.valueOf(ctx.DECIMAL().getText());  }  @Override  public Object visitIdentifierexpression(SimpleBooleanParser.IdentifierexpressionContext ctx) {    return variables.get(ctx.IDENTIFIER().getText());  }  @Override  public Object visitNotexpression(SimpleBooleanParser.NotexpressionContext ctx) {    return !((Boolean)this.visit(ctx.expression()));  }  @Override  public Object visitParenexpression(SimpleBooleanParser.ParenexpressionContext ctx) {    return super.visit(ctx.expression());  }  @Override  public Object visitComparatorexpression(SimpleBooleanParser.ComparatorexpressionContext ctx) {    if (ctx.op.EQ() != null) {      return this.visit(ctx.left).equals(this.visit(ctx.right));    }    else if (ctx.op.LE() != null) {      return asDouble(ctx.left) <= asDouble(ctx.right);    }    else if (ctx.op.GE() != null) {      return asDouble(ctx.left) >= asDouble(ctx.right);    }    else if (ctx.op.LT() != null) {      return asDouble(ctx.left) < asDouble(ctx.right);    }    else if (ctx.op.GT() != null) {      return asDouble(ctx.left) > asDouble(ctx.right);    }    throw new RuntimeException("not implemented: comparator operator " + ctx.op.getText());  }  @Override  public Object visitBinaryexpression(SimpleBooleanParser.BinaryexpressionContext ctx) {    if (ctx.op.AND() != null) {      return asBoolean(ctx.left) && asBoolean(ctx.right);    }    else if (ctx.op.OR() != null) {      return asBoolean(ctx.left) || asBoolean(ctx.right);    }    throw new RuntimeException("not implemented: binary operator " + ctx.op.getText());  }  @Override  public Object visitBoolexpression(SimpleBooleanParser.BoolexpressionContext ctx) {    return Boolean.valueOf(ctx.getText());  }  private boolean asBoolean(SimpleBooleanParser.expressionContext ctx) {    return (boolean)visit(ctx);  }  private double asDouble(SimpleBooleanParser.expressionContext ctx) {    return (double)visit(ctx);  }}

运行

Main

1 > 2-> false1 >= 1.0        -> trueTRUE = FALSE    -> falseFALSE = FALSE   -> trueA OR B          -> trueB    -> falseA = B-> falsec = C-> trueE > D-> trueB OR (c = B OR (A = A AND c = C AND E > D))      -> true(A = a OR B = b OR C = c AND ((D = d AND E = e) OR (F = f AND G = g))) -> true