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hash_example.cc
/************************************************************************/
/* */
/* Centre for Speech Technology Research */
/* University of Edinburgh, UK */
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/************************************************************************/
/* Author: Richard Caley (rjc@cstr.ed.ac.uk) */
/* Date: Tue Apr 29 1997 */
/************************************************************************/
/* */
/* Example of hash table use. */
/* */
/************************************************************************/
#include <cstdlib>
#include <iostream>
#include <cmath>
#include "EST_THash.h"
#include "EST_String.h"
// a very boring thing to do to a pair, see map below
static void look_at(EST_String &s, int &l)
{
(void)s;
(void)l;
cout << ".";
}
int
main(void)
{
// Map from strings to numbers, hashed by default method.
EST_TStringHash<int> lengths(100);
lengths.add_item("fred", 4);
lengths.add_item("bill", 4);
lengths.add_item("harry", 5);
const EST_TStringHash<int> const_lengths = lengths;
// Map from ints to floats. Note, the other way around is alomst
// certainly a mistake.
EST_THash<int,float> logs(100);
logs.add_item(12, log(12.0));
logs.add_item(34, log(34.0));
cout << "length of `fred' = " << lengths.val("fred") << "\n";
cout << "log of 34' = " << logs.val(34) << "\n";
// remove items with the remove_item() method.
logs.remove_item(34);
cout << "now don't know log of 34' = " << logs.val(34) << "\n";
// the second argument to val can be used to
// ask whether the result was actually found. Useful
// when the dummy value returned for an unknown key is
// actually a valid value for the application.
int found;
float val = logs.val(123, found);
cout << "log of 123";
if (found)
cout << " = " << val;
else
cout << " not found";
cout << "\n";
// dump puts out a human readable version of the table for debugging
lengths.dump(cout);
// map calls a function on each pair, in this case just prints one dot per
// pair (see definition of look_at earlier).
lengths.map(look_at);
cout << "\n";
// We can step through the table with an iterator.
EST_THash<EST_String, int>::Entries them;
for(them.begin(const_lengths); them; them++)
{
cout << them->k << " " << them->v << " ";
}
cout << "\n";
EST_THash<EST_String, int>::RwEntries rwthem;
for(rwthem.begin(lengths); rwthem; rwthem++)
{
rwthem->v *= 3;
cout << rwthem->k << " " << rwthem->v << " ";
}
cout << "\n";
return 0;
}
template <> int EST_THash<int, float>::Dummy_Key = 0;
template <> float EST_THash<int, float>::Dummy_Value = 0.0;
#if defined(INSTANTIATE_TEMPLATES)
#include "../base_class/EST_THash.cc"
Instantiate_THash(int,float)
#endif
EST_String
Definition EST_String.h:70
EST_THash
Definition EST_THash.h:96
EST_THash::Entries
EST_TStructIterator< EST_THash< K, V >, IPointer, EST_Hash_Pair< K, V > > Entries
Give the iterator a sensible name.
Definition EST_THash.h:217
EST_TIterator::begin
void begin(const Container &over)
Set the iterator ready to run over this container.
Definition EST_TIterator.h:115
EST_TRwIterator::begin
void begin(Container &over)
Set the iterator ready to run over this container.
Definition EST_TIterator.h:245
EST_TStringHash
Definition EST_THash.h:281