Seven instructive examples how to use Boost Spirit

spirit1_simple.cpp

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+// Example how to use Boost Spirit to parse plain integers and lists of integers
+//
+// test1() parses "5",
+// test2() parses "76131 Karlsruhe",
+// test3() parses "[12345,42,5,]"
+// test4() parses "[12345,42,5]"
+// test5() parses "[12345, 42, 5 ]"
+
+#include <iostream>
+#include <iomanip>
+#include <stdexcept>
+
+#include <boost/spirit/include/qi.hpp>
+
+namespace qi = boost::spirit::qi;
+
+/******************************************************************************/
+// First Example: parse a single integer
+
+void test1()
+{
+    std::string input = "12345";
+    int out_int;
+
+    qi::parse(
+        // input string (iterators)
+        input.begin(), input.end(),
+        // parser grammar
+        qi::int_,
+        // output fields
+        out_int);
+
+    std::cout << "test1() parse result: "
+              << out_int << std::endl;
+}
+
+/******************************************************************************/
+// Parse an integer followed by a space and a string
+
+void test2()
+{
+    std::string input = "76131 Karlsruhe";
+    int out_int;
+    std::string out_string;
+
+    qi::parse(
+        // input string (iterators)
+        input.begin(), input.end(),
+        // parser grammar
+        qi::int_ >> ' ' >> *qi::char_,
+        // output fields
+        out_int, out_string);
+
+    std::cout << "test2() parse result: "
+              << out_int << " " << out_string << std::endl;
+}
+
+/******************************************************************************/
+// Parse a bracketed list of integers
+
+void test3()
+{
+    std::string input = "[12345,42,5,]";
+    std::vector<int> out_int_list;
+
+    qi::parse(
+        // input string (iterators)
+        input.begin(), input.end(),
+        // parser grammar
+        '[' >> *(qi::int_ >> ',') >> ']',
+        // output list
+        out_int_list);
+
+    std::cout << "test3() parse result: size "
+              << out_int_list.size() << std::endl;
+    for (const size_t &i : out_int_list)
+        std::cout << i << std::endl;
+}
+
+/******************************************************************************/
+// Parse a bracketed list of integers without last comma
+
+// Helper to run a parser, check for errors, and capture the results.
+template <typename Parser, typename ... Args>
+void ParseOrDie(const std::string& input, const Parser& p, Args&& ... args)
+{
+    std::string::const_iterator begin = input.begin(), end = input.end();
+    bool ok = qi::parse(begin, end, p, std::forward<Args>(args) ...);
+    if (!ok || begin != end) {
+        std::cout << "Unparseable: "
+                  << std::quoted(std::string(begin, end)) << std::endl;
+        throw std::runtime_error("Parse error");
+    }
+}
+
+void test4(std::string input)
+{
+    std::vector<int> out_int_list;
+
+    ParseOrDie(
+        // input string
+        input,
+        // parser grammar with '%' operator
+        '[' >> (qi::int_ % ',') >> ']',
+        // output list
+        out_int_list);
+
+    std::cout << "test4() parse result: size "
+              << out_int_list.size() << std::endl;
+    for (const size_t &i : out_int_list)
+        std::cout << i << std::endl;
+}
+
+/******************************************************************************/
+// Parse a bracketed list of integers with spaces between symbols
+
+// Helper to run a parser, check for errors, and capture the results.
+template <typename Parser, typename Skipper, typename ... Args>
+void PhraseParseOrDie(
+    const std::string& input, const Parser& p, const Skipper& s,
+    Args&& ... args)
+{
+    std::string::const_iterator begin = input.begin(), end = input.end();
+    boost::spirit::qi::phrase_parse(
+        begin, end, p, s, std::forward<Args>(args) ...);
+    if (begin != end) {
+        std::cout << "Unparseable: "
+                  << std::quoted(std::string(begin, end)) << std::endl;
+        throw std::runtime_error("Parse error");
+    }
+}
+
+void test5(std::string input)
+{
+    std::vector<int> out_int_list;
+
+    PhraseParseOrDie(
+        // input string
+        input,
+        // parser grammar
+        '[' >> (qi::int_ % ',') >> ']',
+        // skip parser
+        qi::space,
+        // output list
+        out_int_list);
+
+    std::cout << "test5() parse result: size "
+              << out_int_list.size() << std::endl;
+    for (const size_t &i : out_int_list)
+        std::cout << i << std::endl;
+}
+
+/******************************************************************************/
+
+int main(int argc, char* argv[])
+{
+    test1();
+    test2();
+    test3();
+    test4(argc >= 2 ? argv[1] : "[12345,42,5]");
+    test5(argc >= 3 ? argv[2] : "[12345, 42, 5]");
+
+    return 0;
+}
+
+/******************************************************************************/