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require File.expand_path('../../../spec_helper', __FILE__)
describe "Integer#[]" do
context "fixnum" do
it "behaves like (n >> b) & 1" do
0b101[1].should == 0
0b101[2].should == 1
end
it "returns 1 if the nth bit is set" do
15[1].should == 1
end
it "returns 1 if the nth bit is set (in two's-complement representation)" do
(-1)[1].should == 1
end
it "returns 0 if the nth bit is not set" do
8[2].should == 0
end
it "returns 0 if the nth bit is not set (in two's-complement representation)" do
(-2)[0].should == 0
end
it "returns 0 if the nth bit is greater than the most significant bit" do
2[3].should == 0
end
it "returns 1 if self is negative and the nth bit is greater than the most significant bit" do
(-1)[3].should == 1
end
it "returns 0 when passed a negative argument" do
3[-1].should == 0
(-1)[-1].should == 0
end
it "calls #to_int to convert the argument to an Integer and returns 1 if the nth bit is set" do
obj = mock('1')
obj.should_receive(:to_int).and_return(1)
2[obj].should == 1
end
it "calls #to_int to convert the argument to an Integer and returns 0 if the nth bit is set" do
obj = mock('0')
obj.should_receive(:to_int).and_return(0)
2[obj].should == 0
end
it "accepts a Float argument and returns 0 if the bit at the truncated value is not set" do
13[1.3].should == 0
end
it "accepts a Float argument and returns 1 if the bit at the truncated value is set" do
13[2.1].should == 1
end
it "raises a TypeError when passed a String" do
lambda { 3["3"] }.should raise_error(TypeError)
end
it "raises a TypeError when #to_int does not return an Integer" do
obj = mock('asdf')
obj.should_receive(:to_int).and_return("asdf")
lambda { 3[obj] }.should raise_error(TypeError)
end
it "calls #to_int to coerce a String to a Bignum and returns 0" do
obj = mock('bignum value')
obj.should_receive(:to_int).and_return(bignum_value)
3[obj].should == 0
end
it "returns 0 when passed a Float in the range of a Bignum" do
3[bignum_value.to_f].should == 0
end
end
context "bignum" do
before :each do
@bignum = bignum_value(4996)
end
it "returns the nth bit in the binary representation of self" do
@bignum[2].should == 1
@bignum[9.2].should == 1
@bignum[21].should == 0
@bignum[0xffffffff].should == 0
@bignum[-0xffffffff].should == 0
end
it "tries to convert the given argument to an Integer using #to_int" do
@bignum[1.3].should == @bignum[1]
(obj = mock('2')).should_receive(:to_int).at_least(1).and_return(2)
@bignum[obj].should == 1
end
it "raises a TypeError when the given argument can't be converted to Integer" do
obj = mock('asdf')
lambda { @bignum[obj] }.should raise_error(TypeError)
obj.should_receive(:to_int).and_return("asdf")
lambda { @bignum[obj] }.should raise_error(TypeError)
end
end
end
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