Rework the Random module

spec/std/random/isaac_spec.cr

@@ -342,7 +342,7 @@ describe "Random::ISAAC" do
 
     m = Random::ISAAC.new seed
     numbers.each do |n|
-      m.next_u32.should eq(n)
+      m.next_u.should eq(n)
     end
   end
 end

spec/std/random/mt19937_spec.cr

@@ -211,7 +211,7 @@ describe "Random::MT19937" do
 
     m = Random::MT19937.new [0x123, 0x234, 0x345, 0x456]
     numbers.each do |n|
-      m.next_u32.should eq(n)
+      m.next_u.should eq(n)
     end
   end
 end

spec/std/random_spec.cr

@@ -1,18 +1,47 @@
 require "spec"
 
+class TestRNG(T)
+  include Random
+
+  def initialize(@data : Array(T))
+    @i = 0
+  end
+
+  def next_u : T
+    i = @i
+    @i = (i + 1) % @data.size
+    @data[i]
+  end
+
+  def reset
+    @i = 0
+  end
+end
+
+RNG_DATA_8  = [234u8, 153u8, 0u8, 0u8, 127u8, 128u8, 255u8, 255u8]
+RNG_DATA_32 = [31541451u32, 0u32, 1u32, 234u32, 342475672u32, 863u32, 0xffffffffu32, 50967465u32]
+RNG_DATA_64 = [148763248732657823u64, 18446744073709551615u64, 0u64,
+  32456325635673576u64, 2456245614625u64, 32452456246u64, 3956529762u64,
+  9823674982364u64, 234253464546456u64, 14345435645646u64]
+
 describe "Random" do
   it "limited number" do
     rand(1).should eq(0)
 
     x = rand(2)
     x.should be >= 0
     x.should be < 2
+
+    # issue 3350
+    5.times do
+      rand(Int64::MAX).should be >= 0
+    end
   end
 
   it "float number" do
     x = rand
-    x.should be > 0
-    x.should be < 1
+    x.should be >= 0
+    x.should be <= 1
   end
 
   it "limited float number" do
@@ -22,23 +51,27 @@ describe "Random" do
   end
 
   it "raises on invalid number" do
-    expect_raises ArgumentError, "incorrect rand value: 0" do
+    expect_raises ArgumentError, "invalid bound for rand: 0" do
       rand(0)
     end
   end
 
   it "does with inclusive range" do
-    rand(1..1).should eq(1)
-    x = rand(1..3)
-    x.should be >= 1
-    x.should be <= 3
+    [1..1, 1..3, 0u8..255u8, -1..1, Int64::MIN..7i64,
+      -7i64..Int64::MAX, 0u64..0u64].each do |range|
+      x = rand(range)
+      x.should be >= range.begin
+      x.should be <= range.end
+    end
   end
 
   it "does with exclusive range" do
-    rand(1...2).should eq(1)
-    x = rand(1...4)
-    x.should be >= 1
-    x.should be < 4
+    [1...2, 1...4, 0u8...255u8, -1...1, Int64::MIN...7i64,
+      -7i64...Int64::MAX, -1i8...0i8].each do |range|
+      x = rand(range)
+      x.should be >= range.begin
+      x.should be < range.end
+    end
   end
 
   it "does with inclusive range of floats" do
@@ -55,9 +88,18 @@ describe "Random" do
   end
 
   it "raises on invalid range" do
-    expect_raises ArgumentError, "incorrect rand value: 1...1" do
+    expect_raises ArgumentError, "invalid range for rand: 1...1" do
       rand(1...1)
     end
+    expect_raises ArgumentError, "invalid range for rand: 1..0" do
+      rand(1..0)
+    end
+    expect_raises ArgumentError, "invalid range for rand: 1.0...1.0" do
+      rand(1.0...1.0)
+    end
+    expect_raises ArgumentError, "invalid range for rand: 1.0..0.0" do
+      rand(1.0..0.0)
+    end
   end
 
   it "allows creating a new default random" do
@@ -67,16 +109,71 @@ describe "Random" do
   end
 
   it "allows creating a new default random with a seed" do
-    rand = Random.new(1234)
-    value1 = rand.rand
-
-    rand = Random.new(1234)
-    value2 = rand.rand
+    values = Array.new(2) do
+      rand = Random.new(1234)
+      {rand.rand, rand.rand(0xffffffffffffffff), rand.rand(2), rand.rand(-5i8..5i8)}
+    end
 
-    value1.should eq(value2)
+    values[0].should eq values[1]
   end
 
   it "gets a random bool" do
     Random::DEFAULT.next_bool.should be_a(Bool)
   end
+
+  it "generates by accumulation" do
+    rng = TestRNG.new([234u8, 153u8, 0u8, 0u8, 127u8, 128u8, 255u8, 255u8])
+    rng.rand(65536).should eq 60057    # 234*0x100 + 153
+    rng.rand(60000).should eq 0        # 0*0x100 + 0
+    rng.rand(30000).should eq 2640     # (127*0x100 + 128) % 30000
+    rng.rand(65535u16).should eq 60057 # 255*0x100 + 255 [skip]-> 234*0x100 + 153
+    rng.reset
+    rng.rand(65537).should eq 38934 # (234*0x10000 + 153*0x100 + 0) % 65537
+    rng.reset
+    rng.rand(32768u16).should eq 27289 # (234*0x100 + 153) % 32768
+  end
+
+  it "generates by truncation" do
+    rng = TestRNG.new([31541451u32, 0u32, 1u32, 234u32, 342475672u32])
+    rng.rand(1).should eq 0
+    rng.rand(10).should eq 0
+    rng.rand(2).should eq 1
+    rng.rand(256u64).should eq 234
+    rng.rand(255u8).should eq 217   # 342475672 % 255
+    rng.rand(65536).should eq 18635 # 31541451 % 65536
+    rng = TestRNG.new([0xffffffffu32, 0u32])
+    rng.rand(0x7fffffff).should eq 0
+  end
+
+  it "generates full-range" do
+    rng = TestRNG.new(RNG_DATA_64)
+    RNG_DATA_64.each do |a|
+      rng.rand(UInt64::MIN..UInt64::MAX).should eq a
+    end
+  end
+
+  it "generates full-range by accumulation" do
+    rng = TestRNG.new(RNG_DATA_8)
+    RNG_DATA_8.each_slice(2) do |(a, b)|
+      expected = a.to_u16 * 0x100u16 + b.to_u16
+      rng.rand(UInt16::MIN..UInt16::MAX).should eq expected
+    end
+  end
+
+  it "generates full-range by truncation" do
+    rng = TestRNG.new(RNG_DATA_32)
+    RNG_DATA_32.each do |a|
+      expected = a % 0x10000
+      rng.rand(UInt16::MIN..UInt16::MAX).should eq expected
+    end
+  end
+
+  it "generates full-range by negation" do
+    rng = TestRNG.new(RNG_DATA_8)
+    RNG_DATA_8.each do |a|
+      expected = a.to_i
+      expected -= 0x100 if a >= 0x80
+      rng.rand(Int8::MIN..Int8::MAX).should eq expected
+    end
+  end
 end