lib: intro `Float::log_base`

[nit.git] / lib / standard / math.nit

diff --git a/lib/standard/math.nit b/lib/standard/math.nit
index 1d1437b..2b55dca 100644 (file)
--- a/lib/standard/math.nit
+++ b/lib/standard/math.nit
@@ -26,27 +26,27 @@ redef class Int
 
        # Returns the result of a binary AND operation on `self` and `i`
        #
-       #    assert 0x10.bin_and(0x01) == 0
+       #     assert 0x10.bin_and(0x01) == 0
        fun bin_and(i: Int): Int is extern "kernel_Int_Int_binand_0"
 
        # Returns the result of a binary OR operation on `self` and `i`
        #
-       #    assert 0x10.bin_or(0x01) == 0x11
+       #     assert 0x10.bin_or(0x01) == 0x11
        fun bin_or(i: Int): Int is extern "kernel_Int_Int_binor_0"
 
        # Returns the result of a binary XOR operation on `self` and `i`
        #
-       #    assert 0x101.bin_xor(0x110) == 0x11
+       #     assert 0x101.bin_xor(0x110) == 0x11
        fun bin_xor(i: Int): Int is extern "kernel_Int_Int_binxor_0"
 
        # Returns the 1's complement of `self`
        #
-       #    assert 0x2F.bin_not == -48
+       #     assert 0x2F.bin_not == -48
        fun bin_not: Int is extern "kernel_Int_Int_binnot_0"
 
        # Returns the square root of `self`
        #
-       #    assert 16.sqrt == 4
+       #     assert 16.sqrt == 4
        fun sqrt: Int `{ return sqrt(recv); `}
 
        # Returns the greatest common divisor of `self` and `o`
@@ -76,17 +76,17 @@ redef class Int
 
        # Is `self` even ?
        #
-       #    assert 12.is_even
+       #     assert 12.is_even
        fun is_even: Bool do return self % 2 == 0
 
        # Is `self` odd ?
        #
-       #    assert not 13.is_even
+       #     assert not 13.is_even
        fun is_odd: Bool do return not is_even
 
        # Returns the `self` raised to the power of `e`.
        #
-       #    assert 2 ** 3 == 8
+       #     assert 2 ** 3 == 8
        fun **(e: Int): Int
        do
                return self.to_f.pow(e.to_f).to_i
@@ -96,10 +96,10 @@ redef class Int
        #
        # Returns `1 * 2 * 3 * ... * self-1 * self`
        #
-       #    assert 0.factorial == 1  # by convention for an empty product
-       #    assert 1.factorial == 1
-       #    assert 4.factorial == 24
-       #    assert 9.factorial == 362880
+       #     assert 0.factorial == 1  # by convention for an empty product
+       #     assert 1.factorial == 1
+       #     assert 4.factorial == 24
+       #     assert 9.factorial == 362880
        fun factorial: Int
        do
                assert self >= 0
@@ -167,13 +167,19 @@ redef class Float
        #     #assert 0.0.pow(9.0) == 0.0
        fun pow(e: Float): Float is extern "kernel_Float_Float_pow_1"
 
-       # Returns the logarithm of `self`.
+       # Natural logarithm of `self`.
        #
        #     assert 0.0.log.is_inf == -1
        #     #assert 1.0.log == 0.0
        fun log: Float is extern "kernel_Float_Float_log_0"
 
-       # Returns **e** raised to `self`.
+       # Logarithm of `self` to base `base`.
+       #
+       #     assert 100.0.log_base(10.0) == 2.0
+       #     assert 256.0.log_base(2.0) == 8.0
+       fun log_base(base: Float): Float do return log/base.log
+
+       # Returns *e* raised to `self`.
        fun exp: Float is extern "kernel_Float_Float_exp_0"
 
        #     assert 1.1.ceil == 2.0
@@ -195,7 +201,7 @@ redef class Float
        #     assert -1.34.round == -1.0
        #     assert -1.67.round == -2.0
        fun round: Float is extern "round"
-       
+
        # Returns a random `Float` in `[0.0 .. self[`.
        fun rand: Float is extern "kernel_Float_Float_rand_0"
 
@@ -220,6 +226,16 @@ redef class Float
        end
 
        private fun is_inf_extern: Bool is extern "isinf"
+
+       # Linear interpolation between `a` and `b` using `self` as weight
+       #
+       # ~~~
+       # assert  0.0.lerp(0.0, 128.0) == 0.0
+       # assert  0.5.lerp(0.0, 128.0) == 64.0
+       # assert  1.0.lerp(0.0, 128.0) == 128.0
+       # assert -0.5.lerp(0.0, 128.0) == -64.0
+       # ~~~
+       fun lerp(a, b: Float): Float do return (1.0 - self) * a + self * b
 end
 
 redef class Collection[ E ]
@@ -238,6 +254,15 @@ redef class Collection[ E ]
        end
 end
 
+redef class SequenceRead[E]
+       # Optimized for large collections using `[]`
+       redef fun rand
+       do
+               assert not is_empty
+               return self[length.rand]
+       end
+end
+
 redef class Sys
        init
        do