feat(math): add logb function

Closes #12112

CHANGELOG.rst

@@ -7,6 +7,10 @@ Notable improvements and fixes
 Deprecations and removed features
 ---------------------------------
 
+Scripting improvements
+----------------------
+- ``math`` gained a new ``logb`` function.
+
 Interactive improvements
 ------------------------
 - When typing immediately after starting fish, the first prompt is now rendered correctly.

doc_src/cmds/math.rst

@@ -156,6 +156,8 @@ Functions
     the base-10 logarithm
 ``log2``
     the base-2 logarithm
+``logb(b,x)``
+    returns the logarithm with base b of x
 ``max``
     returns the largest of the given numbers - this takes an arbitrary number of arguments (but at least one)
 ``min``

src/tinyexpr.rs

@@ -291,6 +291,7 @@ fn npr(n: f64, r: f64) -> f64 {
     (L!("log"), Function::Fn1(f64::log10)),
     (L!("log10"), Function::Fn1(f64::log10)),
     (L!("log2"), Function::Fn1(f64::log2)),
+    (L!("logb"), Function::Fn2(|base, x| x.log(base))),
     (L!("max"), Function::FnN(maximum)),
     (L!("min"), Function::FnN(minimum)),
     (L!("ncr"), Function::Fn2(ncr)),

tests/checks/math.fish

@@ -276,6 +276,21 @@ echo $status
 math 'log2(8)'
 # CHECK: 3
 
+math 'logb(2, 8)'
+# CHECK: 3
+math 'logb(67, 406067677556641)'
+# CHECK: 8
+math 'logb(42, 230539333248)'
+# CHECK: 7
+math 'logb(12, 8916100448256)'
+# CHECK: 12
+math 'logb(3, 5559060566555523)'
+# CHECK: 33
+math 'logb(5, 2384185791015625)'
+# CHECK: 22
+math 'logb(7, 343)'
+# CHECK: 3
+
 # same as sin(cos(2 x pi))
 math sin cos 2 x pi
 # CHECK: 0.841471