conversion from ChebyshevT; close issue #372 (#373)

* conversion from ChebyshevT; close issue #372

* doctest fix

Author: jverzani

Project.toml

@@ -2,7 +2,7 @@ name = "Polynomials"
 uuid = "f27b6e38-b328-58d1-80ce-0feddd5e7a45"
 license = "MIT"
 author = "JuliaMath"
-version = "2.0.19"
+version = "2.0.20"
 
 [deps]
 Intervals = "d8418881-c3e1-53bb-8760-2df7ec849ed5"

docs/src/polynomials/chebyshev.md

@@ -31,7 +31,7 @@ ChebyshevT(1⋅T_0(x) + 3⋅T_2(x) + 4⋅T_3(x))
 
 
 julia> p = convert(Polynomial, c)
-Polynomial(-2.0 - 12.0*x + 6.0*x^2 + 16.0*x^3)
+Polynomial(-2 - 12*x + 6*x^2 + 16*x^3)
 
 julia> convert(ChebyshevT, p)
 ChebyshevT(1.0⋅T_0(x) + 3.0⋅T_2(x) + 4.0⋅T_3(x))

src/polynomials/ChebyshevT.jl

@@ -57,7 +57,8 @@ end
 @register ChebyshevT
 
 function Base.convert(P::Type{<:Polynomial}, ch::ChebyshevT)
-    T = eltype(P)
+
+    T = _eltype(P,ch)
     X = indeterminate(P,ch)
     Q = ⟒(P){T,X}
 

test/ChebyshevT.jl

@@ -166,7 +166,7 @@ end
     # issue 326 evaluate outside of domain
     @test Polynomials.evalpoly(2, c1, false) ≈ fn(2)
     @test Polynomials.evalpoly(3, c1, false) ≈ fn(3)
-    
+
     # GCD
     c1 = ChebyshevT([1, 2, 3])
     c2 = ChebyshevT([3, 2, 1])
@@ -221,6 +221,12 @@ end
     # issue #295
     x = BigFloat[-2/3, -1/3, 1/3, 2/4]
     y = BigFloat[1, 2, 3, 4]
-    fit(ChebyshevT, x, y, 1) 
+    fit(ChebyshevT, x, y, 1)
+
+    # issue #372
+    xs = [0,0,1]
+    @test eltype(convert(Polynomial, ChebyshevT{Float64}(xs))) == Float64
+    @test eltype(convert(Polynomial, ChebyshevT{BigFloat}(xs))) == BigFloat
+    @test eltype(convert(Polynomial{BigFloat}, ChebyshevT(xs))) == BigFloat
 
 end