Create a Hash: Difference between revisions
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#REDIRECT [[Associative array/Creation]] |
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{{task}} |
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Create a Hash object that links keys to values and returns a pre-specified element when a key is unknown. |
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{{maintenance}} |
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==[[C plus plus|C++]]== |
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[[Category:C plus plus]] |
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'''Compiler:''' g++ 4.0.2 |
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#include <map> |
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int |
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main( int argc, char* argv[] ) |
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{ |
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std::map< std::string, std::string > hash ; |
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hash[ "key-1" ] = "val1" ; |
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} |
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==[[C sharp|C#]]== |
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[[Category:C sharp]] |
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Defining a Hash |
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System.Collections.HashTable h = new System.Collections.HashTable(); |
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Adding values |
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h.add( "key1" , "foo" ); |
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h.add( "key2" , "bar" ); |
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or |
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h["key1"] = "foo"; |
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h["key2"] = "bar"; |
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---- |
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Hash in .NET 2.0 |
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Dictionary<string, string> hash = new Dictionary<string,string>(); |
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hash.Add( "key1", "foo" ); |
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or |
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Dictionary<string, string> hash = new Dictionary<string,string>(); |
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hash[ "key1" ] = "foo"; |
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==[[ColdFusion]]== |
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[[Category:ColdFusion]] |
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<cfset myHash = structNew()> |
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<cfset myHash.key1 = "foo"> |
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<cfset myHash["key2"] = "bar"> |
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<cfset myHash.put("key3","java-style")> |
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In ColdFusion, a map is literally a java.util.HashMap, thus the above 3rd method is possible. |
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==[[Common Lisp]]== |
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[[Category:Common Lisp]] |
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(setf my-hash (make-hash-table)) |
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(setf (gethash "H2O" my-hash) "Water") |
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(setf (gethash "HCl" my-hash) "Hydrochloric Acid") |
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(setf (gethash "CO" my-hash) "Carbon Monoxide") |
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==[[Perl]]== |
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[[Category:Perl]] |
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'''Interpeter:''' Perl |
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Defining a Hash |
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# using => key does not need to be quoted unless it contains special chars |
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my %hash = ( |
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key1 => 'val1', |
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'key-2' => 2, |
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three => -238.83, |
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4 => 'val3', |
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); |
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# using , both key and value need to be quoted if containing something non-numeric in nature |
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my %hash = ( |
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'key1', 'val1', |
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'key-2', 2, |
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'three', -238.83, |
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4, 'val3', |
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); |
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Defining a HashRef |
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my $hashref = { |
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key1 => 'val1', |
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'key-2' => 2, |
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three => -238.83, |
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4 => 'val3', |
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} |
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Using a Hash |
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print $hash{'key1'}; |
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$hash{'key1'} = 'val1'; |
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@hash{'key1', 'three'} = ('val1', -238.83); |
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Using a HashRef |
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print $hash->{'key1'}; |
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$hash->{'key1'} = 'val1'; |
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@hash->{'key1', 'three'} = ('val1', -238.83); |
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==[[Python]]== |
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[[Category:Python]] |
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Hashes are a built-in type called dictionaries (or mappings) in Python. |
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hash = dict() # 'dict' is the dictionary type. |
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hash = dict(red="FF0000", green="00FF00", blue="0000FF") |
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hash = { 'key1':1, 'key2':2, } |
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value = hash[key] |
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Numerous methods exist for the mapping type http://docs.python.org/lib/typesmapping.html |
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==[[Ruby]]== |
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[[Category:Ruby]] |
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#a hash object that returns nil for unknown keys |
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hash={} |
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hash[666]='devil' |
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hash[777] # => nil |
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hash[666] # => 'devil' |
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#a hash object that returns 'unknown key' for unknown keys |
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hash=Hash.new('unknown key') |
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hash[666]='devil' |
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hash[777] # => 'unknown key' |
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hash[666] # => 'devil' |
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#a hash object that returns "unknown key #{key}" for unknown keys |
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hash=Hash.new{|h,k|h[k]="unknown key #{k}"} |
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hash[666]='devil' |
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hash[777] # => 'unknown key 777' |
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hash[666] # => 'devil' |
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==[[SmallTalk]]== |
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[[Category:SmallTalk]] |
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"Tested with Dolphin Smalltalk" |
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states := Dictionary new. |
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states at: 'MI' put: 'Michigan'. |
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states at: 'MN' put: 'Minnesota'. |
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==[[Lua]]== |
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[[Category:Lua]] |
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Lua tables are Hashes |
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hash = {} |
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hash[ "key-1" ] = "val1" |
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hash[ "key-2" ] = 1 |
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hash[ "key-3" ] = {} |
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Returns nil on unknown key. |
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Latest revision as of 19:09, 9 March 2013
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