diff options
Diffstat (limited to 'doc/string/index.rdoc')
-rw-r--r-- | doc/string/index.rdoc | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/doc/string/index.rdoc b/doc/string/index.rdoc new file mode 100644 index 0000000000..ce09a37bdf --- /dev/null +++ b/doc/string/index.rdoc @@ -0,0 +1,38 @@ +Returns the integer index of the first match for the given argument, +or +nil+ if none found; +the search of +self+ is forward, and begins at position +offset+ (in characters). + +With string argument +substring+, +returns the index of the first matching substring in +self+: + + 'foo'.index('f') # => 0 + 'foo'.index('o') # => 1 + 'foo'.index('oo') # => 1 + 'foo'.index('ooo') # => nil + 'тест'.index('с') # => 2 + 'こんにちは'.index('ち') # => 3 + +With Regexp argument +regexp+, returns the index of the first match in +self+: + + 'foo'.index(/o./) # => 1 + 'foo'.index(/.o/) # => 0 + +With positive integer +offset+, begins the search at position +offset+: + + 'foo'.index('o', 1) # => 1 + 'foo'.index('o', 2) # => 2 + 'foo'.index('o', 3) # => nil + 'тест'.index('с', 1) # => 2 + 'こんにちは'.index('ち', 2) # => 3 + +With negative integer +offset+, selects the search position by counting backward +from the end of +self+: + + 'foo'.index('o', -1) # => 2 + 'foo'.index('o', -2) # => 1 + 'foo'.index('o', -3) # => 1 + 'foo'.index('o', -4) # => nil + 'foo'.index(/o./, -2) # => 1 + 'foo'.index(/.o/, -2) # => 1 + +Related: String#rindex. |