55 lines
1.5 KiB
Java
55 lines
1.5 KiB
Java
package cobalt.lang;
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// Creates an unambiguous, if ugly, string representation of AST nodes.
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class AstPrinter implements Expr.Visitor<String> {
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String print(Expr expr) {
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return expr.accept(this);
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}
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@Override
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public String visitBinaryExpr(Expr.Binary expr) {
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return parenthesize(expr.operator.lexeme, expr.left, expr.right);
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}
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@Override
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public String visitGroupingExpr(Expr.Grouping expr) {
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return parenthesize("group", expr.expression);
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}
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@Override
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public String visitLiteralExpr(Expr.Literal expr) {
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if (expr.value == null) return "nil";
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return expr.value.toString();
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}
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@Override
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public String visitUnaryExpr(Expr.Unary expr) {
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return parenthesize(expr.operator.lexeme, expr.right);
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}
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private String parenthesize(String name, Expr... exprs) {
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StringBuilder builder = new StringBuilder();
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builder.append("(").append(name);
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for (Expr expr : exprs) {
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builder.append(" ");
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builder.append(expr.accept(this));
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}
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builder.append(")");
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return builder.toString();
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}
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public static void main(String[] args) {
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Expr expression = new Expr.Binary(
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new Expr.Unary(
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new Token(TokenType.MINUS, "-", null, 1),
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new Expr.Literal(123)),
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new Token(TokenType.STAR, "*", null, 1),
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new Expr.Grouping(
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new Expr.Literal(45.67)));
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System.out.println(new AstPrinter().print(expression));
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}
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}
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