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39 lines
1.2 KiB
Plaintext
39 lines
1.2 KiB
Plaintext
Returns the integer position of the first substring that matches the given argument +pattern+,
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or +nil+ if none found.
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When +pattern+ is a string,
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returns the index of the first matching substring in +self+:
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'foo'.index('f') # => 0
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'foo'.index('o') # => 1
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'foo'.index('oo') # => 1
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'foo'.index('ooo') # => nil
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'こんにちは'.index('ち') # => 3
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When +pattern+ is a Regexp, returns the index of the first match in +self+:
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'foo'.index(/o./) # => 1
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'foo'.index(/.o/) # => 0
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When +offset+ is non-negative, begins the search at position +offset+;
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the returned index is relative to the beginning of +self+:
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'bar'.index('r', 0) # => 2
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'bar'.index('r', 1) # => 2
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'bar'.index('r', 2) # => 2
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'bar'.index('r', 3) # => nil
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'bar'.index(/[r-z]/, 0) # => 2
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'こんにちは'.index('ち', 2) # => 3
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With negative integer argument +offset+, selects the search position by counting backward
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from the end of +self+:
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'foo'.index('o', -1) # => 2
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'foo'.index('o', -2) # => 1
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'foo'.index('o', -3) # => 1
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'foo'.index('o', -4) # => nil
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'foo'.index(/o./, -2) # => 1
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'foo'.index(/.o/, -2) # => 1
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Related: see {Querying}[rdoc-ref:String@Querying].
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