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Diffstat (limited to 'spec/ruby/core/integer/element_reference_spec.rb')
| -rw-r--r-- | spec/ruby/core/integer/element_reference_spec.rb | 188 |
1 files changed, 188 insertions, 0 deletions
diff --git a/spec/ruby/core/integer/element_reference_spec.rb b/spec/ruby/core/integer/element_reference_spec.rb new file mode 100644 index 0000000000..cb7e0dc9b0 --- /dev/null +++ b/spec/ruby/core/integer/element_reference_spec.rb @@ -0,0 +1,188 @@ +require_relative '../../spec_helper' + +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 + -> { 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") + -> { 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 + + context "when index and length passed" do + it "returns specified number of bits from specified position" do + 0b101001101[2, 4].should == 0b0011 + 0b101001101[2, 5].should == 0b10011 + 0b101001101[2, 7].should == 0b1010011 + end + + it "ensures n[i, len] equals to (n >> i) & ((1 << len) - 1)" do + n = 0b101001101; i = 2; len = 4 + n[i, len].should == (n >> i) & ((1 << len) - 1) + end + + it "moves start position to the most significant bits when negative index passed" do + 0b000001[-1, 4].should == 0b10 + 0b000001[-2, 4].should == 0b100 + 0b000001[-3, 4].should == 0b1000 + end + + it "ignores negative length" do + 0b101001101[1, -1].should == 0b10100110 + 0b101001101[2, -1].should == 0b1010011 + 0b101001101[3, -1].should == 0b101001 + + 0b101001101[3, -5].should == 0b101001 + 0b101001101[3, -15].should == 0b101001 + 0b101001101[3, -125].should == 0b101001 + end + end + + context "when range passed" do + it "returns bits specified by range" do + 0b101001101[2..5].should == 0b0011 + 0b101001101[2..6].should == 0b10011 + 0b101001101[2..8].should == 0b1010011 + end + + it "ensures n[i..j] equals to (n >> i) & ((1 << (j - i + 1)) - 1)" do + n = 0b101001101; i = 2; j = 5 + n[i..j].should == (n >> i) & ((1 << (j - i + 1)) - 1) + end + + it "ensures n[i..] equals to (n >> i)" do + eval("0b101001101[3..]").should == 0b101001101 >> 3 + end + + it "moves lower boundary to the most significant bits when negative value passed" do + 0b000001[-1, 4].should == 0b10 + 0b000001[-2, 4].should == 0b100 + 0b000001[-3, 4].should == 0b1000 + end + + it "ignores upper boundary smaller than lower boundary" do + 0b101001101[4..1].should == 0b10100 + 0b101001101[4..2].should == 0b10100 + 0b101001101[-4..-5].should == 0b1010011010000 + end + + it "raises FloatDomainError if any boundary is infinity" do + -> { 0x0001[3..Float::INFINITY] }.should raise_error(FloatDomainError, /Infinity/) + -> { 0x0001[-Float::INFINITY..3] }.should raise_error(FloatDomainError, /-Infinity/) + end + + context "when passed (..i)" do + it "returns 0 if all i bits equal 0" do + eval("0b10000[..1]").should == 0 + eval("0b10000[..2]").should == 0 + eval("0b10000[..3]").should == 0 + end + + it "raises ArgumentError if any of i bit equals 1" do + -> { + eval("0b111110[..3]") + }.should raise_error(ArgumentError, /The beginless range for Integer#\[\] results in infinity/) + end + end + 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') + -> { @bignum[obj] }.should raise_error(TypeError) + + obj.should_receive(:to_int).and_return("asdf") + -> { @bignum[obj] }.should raise_error(TypeError) + end + end +end |