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Erik Michaels-Ober (@sferik) RUG::B, 7 May 2015 Symbols

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Symbols are Useless 1. Calling Symbol#to_s on every symbol in your program would not change its semantics. 2. Symbols are an archaic optimization. They were useful 20 years ago, but not today. 3. Symbols and strings have converged into one type.

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"string".freeze.object_id
 ==
 "string".freeze.object_id
 # false on Ruby < 2.1 # true on Ruby >= 2.1 Symbols are ❄ Strings

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def measure init = Time.now yield if block_given? return Time.now - init end Benchmark

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N = 1_000_000 measure { N.times { "string" } } measure { N.times { "string".freeze } } measure { N.times { :symbol } } Benchmark

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string: 0.126956 freeze: 0.056473 symbol: 0.056416 Results

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1. Symbols and frozen strings perform identically. 2. Allocating a million strings takes about twice as long as allocating one string, putting it in into a hash table, and looking it up a million times. 3. You can allocate a million short strings in about a tenth of a second on a typical 2015 laptop computer. Takeaways

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PowerBook 190 33 MHz CPU 8 MB RAM 500 MB HDD $1850 August 1995

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Ruby makes me happy.

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Symbols make me sad.

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:foo == "foo" # true Proposal !"#$%