lib: intro `Float::log_base`

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --git a/lib/standard/math.nit b/lib/standard/math.nit
index eec0cf6..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"