lib: intro `Float::log_base`

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

diff --git a/lib/standard/math.nit b/lib/standard/math.nit
index 14c0e40..2b55dca 100644 (file)
--- a/lib/standard/math.nit
+++ b/lib/standard/math.nit
@@ -167,12 +167,18 @@ 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"
 
+       # 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"
 
@@ -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 ]