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Showing content from https://docs.ruby-lang.org/en/3.4/NilClass.html below:

class NilClass - Documentation for Ruby 3.4

The class of the singleton object nil.

Several of its methods act as operators:

• &

• |

• ===

• =~

• ^

Others act as converters, carrying the concept of nullity to other classes:

• rationalize

• to_a

• to_c

• to_h

• to_r

• to_s

While nil doesn’t have an explicitly defined to_hash method, it can be used in ** unpacking, not adding any keyword arguments.

Another method provides inspection:

• inspect

Finally, there is this query method:

• nil?

static VALUE
false_and(VALUE obj, VALUE obj2)
{
    return Qfalse;
}

Returns false:

false & true       
false & Object.new 

Argument object is evaluated:

false & raise 

#define case_equal rb_equal

Returns true or false.

Like Object#==, if object is an instance of Object (and not an instance of one of its many subclasses).

This method is commonly overridden by those subclasses, to provide meaningful semantics in case statements.

static VALUE
nil_match(VALUE obj1, VALUE obj2)
{
    return Qnil;
}

Returns nil.

This method makes it useful to write:

while gets =~ /re/
  
end

#define false_xor true_and

Returns false if object is nil or false, true otherwise:

nil ^ nil        
nil ^ false      
nil ^ Object.new 

#define false_or true_and

Returns false if object is nil or false, true otherwise:

nil | nil        
nil | false      
nil | Object.new 

static VALUE
nil_inspect(VALUE obj)
{
    return rb_usascii_str_new2("nil");
}

Returns string 'nil':

nil.inspect 

static VALUE
rb_true(VALUE obj)
{
    return Qtrue;
}

Returns true. For all other objects, method nil? returns false.

static VALUE
nilclass_rationalize(int argc, VALUE *argv, VALUE self)
{
    rb_check_arity(argc, 0, 1);
    return nilclass_to_r(self);
}

Returns zero as a Rational:

nil.rationalize 

Argument eps is ignored.

static VALUE
nil_to_a(VALUE obj)
{
    return rb_ary_new2(0);
}

Returns an empty Array.

nil.to_a 

static VALUE
nilclass_to_c(VALUE self)
{
    return rb_complex_new1(INT2FIX(0));
}

Returns zero as a Complex:

nil.to_c 

Always returns zero.

nil.to_f   

static VALUE
nil_to_h(VALUE obj)
{
    return rb_hash_new();
}

Returns an empty Hash.

nil.to_h   

Always returns zero.

nil.to_i   

static VALUE
nilclass_to_r(VALUE self)
{
    return rb_rational_new1(INT2FIX(0));
}

Returns zero as a Rational:

nil.to_r 

VALUE
rb_nil_to_s(VALUE obj)
{
    return rb_cNilClass_to_s;
}

Returns an empty String:

nil.to_s 

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