documented signed

Author: matthias314

docs/src/basics.md

@@ -10,9 +10,10 @@ DocTestSetup = doctestsetup
 deg(::Any)
 ```
 
-## Traits for rings
+## Traits and functions for rings
 
 ```@docs
 LinearCombinations.has_char2
 LinearCombinations.is_domain
+LinearCombinations.signed
 ```

src/basics.jl

@@ -189,6 +189,15 @@ See also [`is_domain`](@ref).
 has_char2(::Type) = false
 has_char2(::Missing) = false
 
+"""
+    LinearCombinations.signed(k, x)
+
+Return a value representing `(-1)^k*x`. The default definition is
+```julia
+signed(k, x::R) where R = has_char2(R) || iseven(k) ? x : -x
+```
+Additional methods may be needed to support more exotic coefficient types.
+"""
 signed(k, x::R) where R = has_char2(R) || iseven(k) ? x : -x
 
 sum0(itr) = sum(itr; init = Zero())