gistfile1.txt

#        (c) Copyright 2013 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

## The ``tables`` module implements an efficient hash table that is
## a mapping from keys to values.
##
## If you are using simple standard types like ``int`` or ``string`` for the
## keys of the table you won't have any problems, but as soon as you try to use
## a more complex object as a key you will be greeted by a strange compiler
## error::
##
##   Error: type mismatch: got (Person)
##   but expected one of:
##   hashes.hash(x: openarray[A]): THash
##   hashes.hash(x: int): THash
##   hashes.hash(x: float): THash
##   …
##
## What is happening here is that the types used for table keys require to have
## a ``hash()`` proc which will convert them to a `THash <hashes.html#THash>`_
## value, and the compiler is listing all the hash functions it knows. After
## you add such a proc for your custom type everything will work. See this
## example:
##
## .. code-block:: nimrod
##   type
##     Person = object
##       firstName, lastName: string
##
##   proc hash(x: Person): THash =
##     ## Piggyback on the already available string hash proc.
##     ##
##     ## Without this proc nothing works!
##     result = x.firstName.hash !& x.lastName.hash
##     result = !$result
##
##   var
##     salaries = initTable[Person, int]()
##     p1, p2: Person
##
##   p1.firstName = "Jon"
##   p1.lastName = "Ross"
##   salaries[p1] = 30_000
##
##   p2.firstName = "소진"
##   p2.lastName = "박"
##   salaries[p2] = 45_000
##
## **Note:** The data types declared here have *value semantics*: This means
## that ``=`` performs a copy of the hash table.