Fix type instability in chebinterp (#19)

* initial commit

* Update interp.jl

* Update src/interp.jl

Co-authored-by: Steven G. Johnson <[email protected]>

---------

Co-authored-by: Steven G. Johnson <[email protected]>

Author: lxvm

src/interp.jl

@@ -80,7 +80,7 @@ function droptol(coefs::Array{<:Any,N}, tol::Real) where {N}
     newsize = ntuple(Val{N}()) do dim
         n = size(coefs, dim)
         while n > 1
-            r = ntuple(i -> i == dim ? (n:n) : (1:size(coefs,i)), Val{N}())
+            r = let n=n; ntuple(i -> i == dim ? (n:n) : (1:size(coefs,i)), Val{N}()); end
             any(c -> infnorm(c) ≥ abstol, @view coefs[CartesianIndices(r)]) && break
             n -= 1
         end

test/runtests.jl

@@ -149,3 +149,8 @@ end
     @test interp([0.1,0.22]) ≈ 3.2*cos(0.55)
     @test chebgradient(interp, [0.1,0.2])[2] == [2*cos(0.55), 0]
 end
+
+@testset "inference" begin
+    @inferred FastChebInterp.droptol(rand(5,5), 0.0)
+    @inferred chebinterp(rand(5,5), (0,0), (1,1))
+end