Tries to convert obj into an array, using to_ary method. Returns the converted array or nil if obj cannot be converted for any reason. This method can be used to check if an argument is an array.
Array.try_convert([1]) #=> [1] Array.try_convert("1") #=> nil if tmp = Array.try_convert(arg) # the argument is an array elsif tmp = String.try_convert(arg) # the argument is a string end
Same as Array#each, but traverses self in reverse order.
a = [ "a", "b", "c" ] a.reverse_each {|x| print x, " " }
produces:
c b a
When invoked with a block, yield all repeated permutations of length n of the elements of the array, then return the array itself.
The implementation makes no guarantees about the order in which the repeated permutations are yielded.
If no block is given, an Enumerator is returned instead.
Examples:
a = [1, 2] a.repeated_permutation(1).to_a #=> [[1], [2]] a.repeated_permutation(2).to_a #=> [[1,1],[1,2],[2,1],[2,2]] a.repeated_permutation(3).to_a #=> [[1,1,1],[1,1,2],[1,2,1],[1,2,2], # [2,1,1],[2,1,2],[2,2,1],[2,2,2]] a.repeated_permutation(0).to_a #=> [[]] # one permutation of length 0
Scans the current string until the match is exhausted yielding each match as it is encountered in the string. A block is not necessary as the results will simply be aggregated into the final array.
"123 456".block_scanf("%d") # => [123, 456]
If a block is given, the value from that is returned from the yield is added to an output array.
"123 456".block_scanf("%d) do |digit,| # the ',' unpacks the Array
digit + 100
end
# => [223, 556]
See Scanf for details on creating a format string.
You will need to require ‘scanf’ to use String#block_scanf
Try to convert obj into a String, using to_str method. Returns converted string or nil if obj cannot be converted for any reason.
String.try_convert("str") #=> "str" String.try_convert(/re/) #=> nil
Returns an array of grapheme clusters in str. This is a shorthand for str.each_grapheme_cluster.to_a.
If a block is given, which is a deprecated form, works the same as each_grapheme_cluster.
Returns the next representable floating point number.
Float::MAX.next_float and Float::INFINITY.next_float is Float::INFINITY.
Float::NAN.next_float is Float::NAN.
For example:
0.01.next_float #=> 0.010000000000000002 1.0.next_float #=> 1.0000000000000002 100.0.next_float #=> 100.00000000000001 0.01.next_float - 0.01 #=> 1.734723475976807e-18 1.0.next_float - 1.0 #=> 2.220446049250313e-16 100.0.next_float - 100.0 #=> 1.4210854715202004e-14 f = 0.01; 20.times { printf "%-20a %s\n", f, f.to_s; f = f.next_float } #=> 0x1.47ae147ae147bp-7 0.01 # 0x1.47ae147ae147cp-7 0.010000000000000002 # 0x1.47ae147ae147dp-7 0.010000000000000004 # 0x1.47ae147ae147ep-7 0.010000000000000005 # 0x1.47ae147ae147fp-7 0.010000000000000007 # 0x1.47ae147ae148p-7 0.010000000000000009 # 0x1.47ae147ae1481p-7 0.01000000000000001 # 0x1.47ae147ae1482p-7 0.010000000000000012 # 0x1.47ae147ae1483p-7 0.010000000000000014 # 0x1.47ae147ae1484p-7 0.010000000000000016 # 0x1.47ae147ae1485p-7 0.010000000000000018 # 0x1.47ae147ae1486p-7 0.01000000000000002 # 0x1.47ae147ae1487p-7 0.010000000000000021 # 0x1.47ae147ae1488p-7 0.010000000000000023 # 0x1.47ae147ae1489p-7 0.010000000000000024 # 0x1.47ae147ae148ap-7 0.010000000000000026 # 0x1.47ae147ae148bp-7 0.010000000000000028 # 0x1.47ae147ae148cp-7 0.01000000000000003 # 0x1.47ae147ae148dp-7 0.010000000000000031 # 0x1.47ae147ae148ep-7 0.010000000000000033 f = 0.0 100.times { f += 0.1 } f #=> 9.99999999999998 # should be 10.0 in the ideal world. 10-f #=> 1.9539925233402755e-14 # the floating point error. 10.0.next_float-10 #=> 1.7763568394002505e-15 # 1 ulp (unit in the last place). (10-f)/(10.0.next_float-10) #=> 11.0 # the error is 11 ulp. (10-f)/(10*Float::EPSILON) #=> 8.8 # approximation of the above. "%a" % 10 #=> "0x1.4p+3" "%a" % f #=> "0x1.3fffffffffff5p+3" # the last hex digit is 5. 16 - 5 = 11 ulp.
Returns the previous representable floating point number.
(-Float::MAX).prev_float and (-Float::INFINITY).prev_float is -Float::INFINITY.
Float::NAN.prev_float is Float::NAN.
For example:
0.01.prev_float #=> 0.009999999999999998 1.0.prev_float #=> 0.9999999999999999 100.0.prev_float #=> 99.99999999999999 0.01 - 0.01.prev_float #=> 1.734723475976807e-18 1.0 - 1.0.prev_float #=> 1.1102230246251565e-16 100.0 - 100.0.prev_float #=> 1.4210854715202004e-14 f = 0.01; 20.times { printf "%-20a %s\n", f, f.to_s; f = f.prev_float } #=> 0x1.47ae147ae147bp-7 0.01 # 0x1.47ae147ae147ap-7 0.009999999999999998 # 0x1.47ae147ae1479p-7 0.009999999999999997 # 0x1.47ae147ae1478p-7 0.009999999999999995 # 0x1.47ae147ae1477p-7 0.009999999999999993 # 0x1.47ae147ae1476p-7 0.009999999999999992 # 0x1.47ae147ae1475p-7 0.00999999999999999 # 0x1.47ae147ae1474p-7 0.009999999999999988 # 0x1.47ae147ae1473p-7 0.009999999999999986 # 0x1.47ae147ae1472p-7 0.009999999999999985 # 0x1.47ae147ae1471p-7 0.009999999999999983 # 0x1.47ae147ae147p-7 0.009999999999999981 # 0x1.47ae147ae146fp-7 0.00999999999999998 # 0x1.47ae147ae146ep-7 0.009999999999999978 # 0x1.47ae147ae146dp-7 0.009999999999999976 # 0x1.47ae147ae146cp-7 0.009999999999999974 # 0x1.47ae147ae146bp-7 0.009999999999999972 # 0x1.47ae147ae146ap-7 0.00999999999999997 # 0x1.47ae147ae1469p-7 0.009999999999999969 # 0x1.47ae147ae1468p-7 0.009999999999999967
Returns default external encoding.
The default external encoding is used by default for strings created from the following locations:
File data read from disk
While strings created from these locations will have this encoding, the encoding may not be valid. Be sure to check String#valid_encoding?.
File data written to disk will be transcoded to the default external encoding when written.
The default external encoding is initialized by the locale or -E option.
Sets default external encoding. You should not set Encoding::default_external in ruby code as strings created before changing the value may have a different encoding from strings created after the value was changed., instead you should use ruby -E to invoke ruby with the correct default_external.
See Encoding::default_external for information on how the default external encoding is used.
Returns default internal encoding. Strings will be transcoded to the default internal encoding in the following places if the default internal encoding is not nil:
File data read from disk
Strings returned from Readline
Strings returned from SDBM
Values from ENV
Values in ARGV including $PROGRAM_NAME
Additionally String#encode and String#encode! use the default internal encoding if no encoding is given.
The locale encoding (__ENCODING__), not default_internal, is used as the encoding of created strings.
Encoding::default_internal is initialized by the source file’s internal_encoding or -E option.
Sets default internal encoding or removes default internal encoding when passed nil. You should not set Encoding::default_internal in ruby code as strings created before changing the value may have a different encoding from strings created after the change. Instead you should use ruby -E to invoke ruby with the correct default_internal.
See Encoding::default_internal for information on how the default internal encoding is used.
Returns the locale charmap name. It returns nil if no appropriate information.
Debian GNU/Linux LANG=C Encoding.locale_charmap #=> "ANSI_X3.4-1968" LANG=ja_JP.EUC-JP Encoding.locale_charmap #=> "EUC-JP" SunOS 5 LANG=C Encoding.locale_charmap #=> "646" LANG=ja Encoding.locale_charmap #=> "eucJP"
The result is highly platform dependent. So Encoding.find(Encoding.locale_charmap) may cause an error. If you need some encoding object even for unknown locale, Encoding.find(“locale”) can be used.
Returns formatted string of exception. The returned string is formatted using the same format that Ruby uses when printing an uncaught exceptions to stderr.
If highlight is true the default error handler will send the messages to a tty.
order must be either of :top or :bottom, and places the error message and the innermost backtrace come at the top or the bottom.
The default values of these options depend on $stderr and its tty? at the timing of a call.
Returns any backtrace associated with the exception. This method is similar to Exception#backtrace, but the backtrace is an array of Thread::Backtrace::Location.
Now, this method is not affected by Exception#set_backtrace().
Return a list of the local variable names defined where this NameError exception was raised.
Internal use only.
Creates instance variables and corresponding methods that return the value of each instance variable. Equivalent to calling “attr:name” on each name in turn. String arguments are converted to symbols.
Creates an accessor method to allow assignment to the attribute symbol.id2name. String arguments are converted to symbols.
Checks for a constant with the given name in mod. If inherit is set, the lookup will also search the ancestors (and Object if mod is a Module).
The value of the constant is returned if a definition is found, otherwise a NameError is raised.
Math.const_get(:PI) #=> 3.14159265358979
This method will recursively look up constant names if a namespaced class name is provided. For example:
module Foo; class Bar; end end Object.const_get 'Foo::Bar'
The inherit flag is respected on each lookup. For example:
module Foo class Bar VAL = 10 end class Baz < Bar; end end Object.const_get 'Foo::Baz::VAL' # => 10 Object.const_get 'Foo::Baz::VAL', false # => NameError
If the argument is not a valid constant name a NameError will be raised with a warning “wrong constant name”.
Object.const_get 'foobar' #=> NameError: wrong constant name foobar
Returns true if the given week date is valid, and false if not.
Date.valid_commercial?(2001,5,6) #=> true Date.valid_commercial?(2001,5,8) #=> false
See also ::jd and ::commercial.
Try to convert obj into an IO, using to_io method. Returns converted IO or nil if obj cannot be converted for any reason.
IO.try_convert(STDOUT) #=> STDOUT IO.try_convert("STDOUT") #=> nil require 'zlib' f = open("/tmp/zz.gz") #=> #<File:/tmp/zz.gz> z = Zlib::GzipReader.open(f) #=> #<Zlib::GzipReader:0x81d8744> IO.try_convert(z) #=> #<File:/tmp/zz.gz>
Closes the read end of a duplex I/O stream (i.e., one that contains both a read and a write stream, such as a pipe). Will raise an IOError if the stream is not duplexed.
f = IO.popen("/bin/sh","r+") f.close_read f.readlines
produces:
prog.rb:3:in `readlines': not opened for reading (IOError) from prog.rb:3
Calling this method on closed IO object is just ignored since Ruby 2.3.
Closes the write end of a duplex I/O stream (i.e., one that contains both a read and a write stream, such as a pipe). Will raise an IOError if the stream is not duplexed.
f = IO.popen("/bin/sh","r+") f.close_write f.print "nowhere"
produces:
prog.rb:3:in `write': not opened for writing (IOError) from prog.rb:3:in `print' from prog.rb:3
Calling this method on closed IO object is just ignored since Ruby 2.3.