When invoked with a block, yield all permutations of length n of the elements of the array, then return the array itself.
If n is not specified, yield all permutations of all elements.
The implementation makes no guarantees about the order in which the permutations are yielded.
If no block is given, an Enumerator is returned instead.
Examples:
a = [1, 2, 3] a.permutation.to_a #=> [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]] a.permutation(1).to_a #=> [[1],[2],[3]] a.permutation(2).to_a #=> [[1,2],[1,3],[2,1],[2,3],[3,1],[3,2]] a.permutation(3).to_a #=> [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]] a.permutation(0).to_a #=> [[]] # one permutation of length 0 a.permutation(4).to_a #=> [] # no permutations of length 4
When invoked with a block, yields all combinations of length n of elements from the array and then returns the array itself.
The implementation makes no guarantees about the order in which the combinations are yielded.
If no block is given, an Enumerator is returned instead.
Examples:
a = [1, 2, 3, 4] a.combination(1).to_a #=> [[1],[2],[3],[4]] a.combination(2).to_a #=> [[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]] a.combination(3).to_a #=> [[1,2,3],[1,2,4],[1,3,4],[2,3,4]] a.combination(4).to_a #=> [[1,2,3,4]] a.combination(0).to_a #=> [[]] # one combination of length 0 a.combination(5).to_a #=> [] # no combinations of length 5
By using binary search, finds a value from this array which meets the given condition in O(log n) where n is the size of the array.
You can use this method in two modes: a find-minimum mode and a find-any mode. In either case, the elements of the array must be monotone (or sorted) with respect to the block.
In find-minimum mode (this is a good choice for typical use cases), the block must always return true or false, and there must be an index i (0 <= i <= ary.size) so that:
the block returns false for any element whose index is less than i, and
the block returns true for any element whose index is greater than or equal to i.
This method returns the i-th element. If i is equal to ary.size, it returns nil.
ary = [0, 4, 7, 10, 12] ary.bsearch {|x| x >= 4 } #=> 4 ary.bsearch {|x| x >= 6 } #=> 7 ary.bsearch {|x| x >= -1 } #=> 0 ary.bsearch {|x| x >= 100 } #=> nil
In find-any mode (this behaves like libc’s bsearch(3)), the block must always return a number, and there must be two indices i and j (0 <= i <= j <= ary.size) so that:
the block returns a positive number for ary if 0 <= k < i,
the block returns zero for ary if i <= k < j, and
the block returns a negative number for ary if j <= k < ary.size.
Under this condition, this method returns any element whose index is within i…j. If i is equal to j (i.e., there is no element that satisfies the block), this method returns nil.
ary = [0, 4, 7, 10, 12] # try to find v such that 4 <= v < 8 ary.bsearch {|x| 1 - x / 4 } #=> 4 or 7 # try to find v such that 8 <= v < 10 ary.bsearch {|x| 4 - x / 2 } #=> nil
You must not mix the two modes at a time; the block must always return either true/false, or always return a number. It is undefined which value is actually picked up at each iteration.
Returns a Hash containing implementation-dependent counters inside the VM.
This hash includes information about method/constant cache serials:
{
:global_method_state=>251,
:global_constant_state=>481,
:class_serial=>9029
}
The contents of the hash are implementation specific and may be changed in the future.
This method is only expected to work on C Ruby.
The primary interface to this library. Use to setup delegation when defining your class.
class MyClass < DelegateClass(ClassToDelegateTo) # Step 1 def initialize super(obj_of_ClassToDelegateTo) # Step 2 end end
Here’s a sample of use from Tempfile which is really a File object with a few special rules about storage location and when the File should be deleted. That makes for an almost textbook perfect example of how to use delegation.
class Tempfile < DelegateClass(File) # constant and class member data initialization... def initialize(basename, tmpdir=Dir::tmpdir) # build up file path/name in var tmpname... @tmpfile = File.open(tmpname, File::RDWR|File::CREAT|File::EXCL, 0600) # ... super(@tmpfile) # below this point, all methods of File are supported... end # ... end
Returns a string containing the character represented by the int‘s value according to encoding.
65.chr #=> "A" 230.chr #=> "\xE6" 255.chr(Encoding::UTF_8) #=> "\u00FF"
Returns int truncated (toward zero) to a precision of ndigits decimal digits (default: 0).
When the precision is negative, the returned value is an integer with at least ndigits.abs trailing zeros.
Returns self when ndigits is zero or positive.
1.truncate #=> 1 1.truncate(2) #=> 1 18.truncate(-1) #=> 10 (-18).truncate(-1) #=> -10
Returns the remainder after dividing int by numeric.
x.remainder(y) means x-y*(x/y).truncate.
5.remainder(3) #=> 2 -5.remainder(3) #=> -2 5.remainder(-3) #=> 2 -5.remainder(-3) #=> -2 5.remainder(1.5) #=> 0.5
See Numeric#divmod.
Returns the absolute value of int.
(-12345).abs #=> 12345 -12345.abs #=> 12345 12345.abs #=> 12345
Integer#magnitude is an alias for Integer#abs.
Returns self.
Returns 1.
Returns the value as a rational. The optional argument eps is always ignored.
Returns the imaginary part.
Complex(7).imaginary #=> 0 Complex(9, -4).imaginary #=> -4
Returns the absolute part of its polar form.
Complex(-1).abs #=> 1 Complex(3.0, -4.0).abs #=> 5.0
Returns the numerator.
1 2 3+4i <- numerator
- + -i -> ----
2 3 6 <- denominator
c = Complex('1/2+2/3i') #=> ((1/2)+(2/3)*i)
n = c.numerator #=> (3+4i)
d = c.denominator #=> 6
n / d #=> ((1/2)+(2/3)*i)
Complex(Rational(n.real, d), Rational(n.imag, d))
#=> ((1/2)+(2/3)*i)
See denominator.
Returns the denominator (lcm of both denominator - real and imag).
See numerator.
Returns the value as a rational if possible (the imaginary part should be exactly zero).
Complex(1.0/3, 0).rationalize #=> (1/3) Complex(1, 0.0).rationalize # RangeError Complex(1, 2).rationalize # RangeError
See to_r.
Returns zero as a rational. The optional argument eps is always ignored.
Returns zero.
Returns zero.
Returns self.
Returns the absolute value of num.
12.abs #=> 12 (-34.56).abs #=> 34.56 -34.56.abs #=> 34.56
Numeric#magnitude is an alias for Numeric#abs.