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/*
* File: foreach.h
* ---------------
* This file defines the <code>foreach</code> keyword, which implements
* a substitute for the range-based <code>for</code> loop from C++11.
* All iterable classes in the Stanford libraries import this file, so
* clients don't ordinarily need to do so explicitly. This version of
* <code>foreach</code> also supports C++ strings and arrays.
*/
#ifndef _foreach_h
#define _foreach_h
/*
* Statement: foreach
* Usage: foreach (type var in collection) { ... }
* -----------------------------------------------
* The <code>foreach</code> statement steps through the elements in
* a collection. It works correctly with the collection classes in
* both the Standard Template Library and the Stanford C++ libraries,
* but can also be used with C++ strings and statically initialized
* arrays.
*
* <p>The following code, for example, prints every element in the
* string vector <code>lines</code>:
*
*<pre>
* foreach (string str in lines) {
* cout << str << endl;
* }
*</pre>
*
* Similarly, the following function calculates the sum of the character
* codes in a string:
*
*<pre>
* int sumCharacterCodes(string str) {
* int sum = 0;
* foreach (char ch in str) sum += ch;
* return sum;
* }
*</pre>
*
* As a simplification when iterating over maps, the <code>foreach</code>
* macro iterates through the keys rather than the key/value pairs.
*/
/* Private section */
/**********************************************************************/
/* Note: Everything below this point in the file is logically part */
/* of the implementation and should not be of interest to clients. */
/**********************************************************************/
#include <iterator>
#include <map>
#include <cstddef>
#include <cstring>
/* These #includes are for files that contain "in" as a token */
#include <ios>
#include <fstream>
#include <sstream>
using namespace std;
/* Redefine the ios constants (one of which is "in") */
static const ios::openmode IOS_APP = ios::app;
static const ios::openmode IOS_ATE = ios::ate;
static const ios::openmode IOS_BINARY = ios::binary;
static const ios::openmode IOS_IN = ios::in;
static const ios::openmode IOS_OUT = ios::out;
static const ios::openmode IOS_TRUNC = ios::trunc;
/* Private implementation namespace */
namespace _fe {
struct Range {
virtual ~Range() { };
};
template <typename T>
struct ArrayRange : Range {
ArrayRange(const T *begin, const T *end) : iter(begin), end(end) { }
const T *iter;
const T *end;
};
template <typename CType>
struct CRange : Range {
CRange(const CType& c) :
cont(c), iter(cont.begin()), end(cont.end()) { }
CType cont;
typename CType::iterator iter, end;
};
template <typename KT, typename VT, typename CT, typename AT>
struct MapRange : Range {
MapRange(const map<KT,VT,CT,AT> & c) :
cont(c), iter(cont.begin()), end(cont.end()) { }
map<KT,VT,CT,AT> cont;
typename map<KT,VT,CT,AT>::iterator iter, end;
};
/*
* The State struct glues together all of these pieces and
* stores all of the information throughout the loops.
*/
struct State {
State() : state(0), itr(NULL) { }
~State() { delete itr; }
int state;
Range *itr;
};
/* General hook function */
template <typename DowncastType, typename ValueType>
ValueType HookImpl(State& fe) {
DowncastType *ip = (DowncastType *) fe.itr;
if (ip->iter == ip->end) {
fe.state = 2;
return ValueType();
}
fe.state = 1;
ValueType vp = *ip->iter; /* Subtle implementation note: */
++ip->iter; /* Using *ip->iter++ here would */
return vp; /* require copying the iterator. */
}
/* Foreach implementation for containers */
template <typename CType>
CRange<CType> *Init(State & fe, const CType & collection) {
fe.itr = new CRange<CType>(collection);
return (CRange<CType>*) fe.itr;
}
template <typename CType>
typename iterator_traits<typename CType::iterator>::value_type
Hook(State & fe, CRange<CType> *) {
return HookImpl<CRange<CType>,
typename iterator_traits<typename CType::iterator>::value_type>(fe);
}
/* For maps */
template <typename K, typename V, typename C, typename A>
MapRange<K,V,C,A> *Init(State & fe, const map<K,V,C,A> & collection) {
fe.itr = new MapRange<K,V,C,A>(collection);
return (MapRange<K,V,C,A>*) fe.itr;
}
template <typename DowncastType, typename ValueType>
ValueType MapHookImpl(State & fe) {
DowncastType *ip = (DowncastType *) fe.itr;
if (ip->iter == ip->end) {
fe.state = 2;
return ValueType();
}
fe.state = 1;
ValueType key = ip->iter->first;
++ip->iter;
return key;
}
template <typename K, typename V, typename C, typename A>
K Hook(State & fe, MapRange<K,V,C,A> *) {
return MapHookImpl<MapRange<K,V,C,A>,K>(fe);
}
/* For C strings */
template <size_t n>
ArrayRange<char> *Init(State & fe, char (&str)[n]) {
fe.itr = new ArrayRange<char>(str, str + strlen(str));
return (ArrayRange<char>*) fe.itr;
}
template <size_t n>
ArrayRange<char> *Init(State & fe, const char (&str)[n]) {
fe.itr = new ArrayRange<char>(str, str + strlen(str));
return (ArrayRange<char>*) fe.itr;
}
/* For arrays */
template <typename T, size_t n>
ArrayRange<T> *Init(State & fe, T (&arr)[n]) {
fe.itr = new ArrayRange<T>(arr, arr + n);
return (ArrayRange<T>*) fe.itr;
}
template <typename T, size_t n>
ArrayRange<T> *Init(State & fe, const T (&arr)[n]) {
fe.itr = new ArrayRange<T>(arr, arr + n);
return (ArrayRange<T>*) fe.itr;
}
template <typename T>
T Hook(State& fe, ArrayRange<T>*) {
return HookImpl<ArrayRange<T>, T>(fe);
}
}
/* The actual foreach and in macros */
#define foreach(arg) \
for (_fe::State _fe; _fe.state < 2; ) \
for (arg)); _fe.state++ == 1; _fe.state = 0)
#define in = _fe::Hook(_fe, _fe.state != 0 ? NULL : _fe::Init(_fe,
#endif
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