lib/utils: build s-expression programmatically building
Allow for programmatically buildings sexps, rather that using raw strings.
This commit is contained in:
Dirk-Jan C. Binnema
252
lib/utils/mu-sexp.hh
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252
lib/utils/mu-sexp.hh
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/*
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** Copyright (C) 2020 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
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**
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** This program is free software; you can redistribute it and/or modify it
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** under the terms of the GNU General Public License as published by the
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** Free Software Foundation; either version 3, or (at your option) any
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** later version.
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**
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** This program is distributed in the hope that it will be useful,
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** but WITHOUT ANY WARRANTY; without even the implied warranty of
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** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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** GNU General Public License for more details.
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**
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** You should have received a copy of the GNU General Public License
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** along with this program; if not, write to the Free Software Foundation,
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** Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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**
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*/
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#ifndef MU_SEXP_HH__
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#define MU_SEXP_HH__
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#include <string>
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#include <vector>
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#include <type_traits>
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#include "utils/mu-utils.hh"
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#include "utils/mu-error.hh"
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namespace Mu {
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namespace Sexp {
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/// Simple s-expression parser & builder that parses lists () and atoms (strings
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/// ("-quoted), (positive) integers ([0..9]+) and symbol starting with alpha or
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/// ':', then alphanum and '-')
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///
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/// (:foo (1234 "bar" nil) :quux (a b c))
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/// Parse node
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struct Node {
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/// Node type
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enum struct Type { List, String, Number, Symbol };
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/**
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* Make a node of out of an s-expression string.
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*
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* @param expr a string containing an s-expression
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*
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* @return the parsed s-expression, or throw Error.
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*/
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static Node make (const std::string& expr);
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/**
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* Make a node for a string/integer/symbol/list value
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*
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* @param val some value
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*
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* @return a node
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*/
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static Node make_string (std::string&& val) { return Node{Type::String, std::move(val)}; }
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static Node make_string (const std::string& val) { return Node{Type::String, std::string{val}}; }
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static Node make_number (int val) { return Node{Type::Number, format("%d", val)}; }
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static Node make_symbol (std::string&& val) { return Node{Type::Symbol, std::move(val)}; }
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/// sequence of node objects
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struct Seq {
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/**
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* Add an item to a node-sequence.
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*
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* @param node item to add; moved/consumed.
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*/
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void add(Node&& node) {nodes_.emplace_back(std::move(node));}
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void add(Seq&& seq) {add(make_list(std::move(seq)));}
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void add(std::string&& s) {add(make_string(std::move(s)));}
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void add(int i) {add(make_number(i));}
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// disambiguate.
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void add_symbol(std::string&& s) {add(make_symbol(std::move(s)));}
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/**
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* Add a property to tne node sequence; i.e. a property-symbol
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* (starting with ':') and some node
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*
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* @param name name (must start with ":"), and some value or list
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* @param val
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*/
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template<typename T> void add_prop(std::string&& name, T&& val) {
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if (name.empty() || name[0] != ':')
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throw Error{Error::Code::InvalidArgument,
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"property names must start with ':'"};
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add(make_symbol(std::move(name)));
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add(std::move(val));
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}
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// deliberately limited stl-like
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/**
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* Is this an empty sequence?
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*
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* @return true or false
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*/
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bool empty() const {return nodes_.empty();}
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/**
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* Get the number of elsements in the sequence
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*
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* @return number of elmement.
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*/
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size_t size() const {return nodes_.size();}
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/**
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* Get begin iterator of the sequence
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*
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* @return iterator
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*/
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const auto begin() const { return nodes_.begin(); }
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/**
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* Get the end iterator of the sequnce
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*
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* @return an iterator
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*/
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const auto end() const { return nodes_.end(); }
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/**
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* Get a const ref to the item at idx.
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*
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* @param idx index, must be < size()
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*
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* @return const ref to the item.
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*/
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const auto at(size_t idx) const { return nodes_.at(idx);}
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private:
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std::vector<Node> nodes_;
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};
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/**
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* Make a list node from a sequence
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*
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* @param seq a sequence of nodes
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*
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* @return a node
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*/
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static Node make_list (Seq&& seq) { return Node{std::move(seq)}; }
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/**
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* Convert a Sexp::Node to its string representation
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*
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* @return the string representation
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*/
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std::string to_string() const;
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/**
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* Return the type of this Node.
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*
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* @return the type
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*/
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Type type() const { return type_; }
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/// Some type helpers
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bool is_list() const { return type() == Type::List; };
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bool is_string() const { return type() == Type::String; }
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bool is_number() const { return type() == Type::Number; }
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bool is_symbol() const { return type() == Type::Symbol; }
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bool is_nil() const { return is_symbol() && value() == "nil"; }
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bool is_t() const { return is_symbol() && value() == "t"; }
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/**
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* The elements of this node; invalid unless this is a list node.
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*
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* @return
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*/
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const Seq& elements() const {
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if (type() != Type::List)
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throw Error(Error::Code::InvalidArgument, "no elements for non-list");
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return seq_;
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}
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/**
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* The value of this node; invalid for list nodes.
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*
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* @return
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*/
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const std::string& value() const {
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if (type_ == Type::List)
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throw Error(Error::Code::InvalidArgument, "no value for list");
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return value_;
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}
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private:
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/**
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* Construct a new non-list node
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*
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* @param typearg the type of node
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* @param valuearg the value
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*/
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Node(Type typearg, std::string&& valuearg):
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type_{typearg}, value_{std::move(valuearg)} {
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if (typearg == Type::List)
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throw Error(Error::Code::Parsing,
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"atomic type cannot be a <list>");
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}
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/**
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* Construct a list node
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*
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* @param kids the list's children
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*/
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explicit Node(Seq&& seq):
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type_{Type::List}, seq_{std::move(seq)}
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{}
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const Type type_; /**< Type of node */
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const std::string value_; /**< String value of node (only for
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* non-Type::Lst)*/
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const Seq seq_; /**< Children of node (only for
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* Type::Lst) */
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};
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static inline std::ostream&
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operator<<(std::ostream& os, Sexp::Node::Type id)
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{
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switch (id) {
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case Sexp::Node::Type::List: os << "<list>"; break;
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case Sexp::Node::Type::String: os << "<string>"; break;
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case Sexp::Node::Type::Number: os << "<number>"; break;
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case Sexp::Node::Type::Symbol: os << "<symbol>"; break;
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default: throw std::runtime_error ("unknown node type");
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}
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return os;
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}
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static inline std::ostream&
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operator<<(std::ostream& os, const Sexp::Node& node)
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{
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os << node.to_string();
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return os;
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}
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} // Sexp
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} // Mu
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#endif /* MU_SEXP_HH__ */
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