Tuples are the most basic infrastructure that the framework builds with. This sub-library provides a mechanism to bundle objects of arbitrary types in a single structure. Tuples hold heterogeneous types up to a predefined maximum.
Only the most basic functionality needed are provided. This is a straight-forward and extremely lean and mean library. Unlike other recursive list-like tuple implementations, this tuple library implementation uses simple structs similar to std::pair with specialization for 0 to N tuple elements, where N is a predefined constant. There are only 4 tuple operations to learn:
Here are examples on how to construct tuples:
typedef tuple<int, char> t1_t; typedef tuple<int, std::string, double> t2_t; // this tuple has an int and char members t1_t t1(3, 'c'); // this tuple has an int, std::string and double members t2_t t2(3, "hello", 3.14);
2) Member access
A member in a tuple can be accessed using the tuple's operator by specifying the Nth tuple_index. Here are some examples:
tuple_index<0> ix0; // 0th index == 1st item tuple_index<1> ix1; // 1st index == 2nd item tuple_index<2> ix2; // 2nd index == 3rd item // Note zero based indexing. 0 = 1st item, 1 = 2nd item t1[ix0] = 33; // sets the int member of the tuple t1 t2[ix2] = 6e6; // sets the double member of the tuple t2 t1[ix1] = 'a'; // sets the char member of the tuple t1
Access to out of bound indexes returns a nil_t value.
3) Member type inquiry
The type of an individual member can be queried. Example:
Refers to the type of the second member (again note zero based indexing, hence 0 = 1st item, 1 = 2nd item) of the tuple.
Access to out of bound indexes returns a nil_t type.
4) Tuple length
The number of elements in a tuple can be queried. Example:
int n = t1.length;
gets the number of elements in tuple t1.
length is a static constant. Thus, TupleT::length also works. Example:
int n = t1_t::length;
Copyright © 2001-2002 Joel de Guzman
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