Sometimes when working with tables there is a natural value to use as the entry in all but a few cases. The GeneralSparseTable constructor can be used to provide any table type with a default value for entries. See TableXmpPage for general information about tables.
Suppose we launched a fund-raising campaign to raise fifty thousand dollars. To record the contributions, we want a table with strings as keys (for the names) and integer entries (for the amount). In a data base of cash contributions, unless someone has been explicitly entered, it is reasonable to assume they have made a zero dollar contribution.
This creates a keyed access file with default entry 0.
patrons: GeneralSparseTable(String, Integer, KeyedAccessFile(Integer),
- := table() ;
Type: GeneralSparseTable(String,Integer,KeyedAccessFile Integer,0)
Now patrons can be used just as any other table. Here we record two gifts.
patrons."Smith" := 10500
patrons."Jones" := 22000
Now let us look up the size of the contributions from Jones and Stingy.
Have we met our seventy thousand dollar goal?
reduce(+, entries patrons)
So the project is cancelled and we can delete the data base:
)system rm -r kaf*.sdata