Add eltype for NLPModels (#481)

Author: tmigot

src/nlp/utils.jl

@@ -141,3 +141,10 @@ macro default_counters(Model, inner)
   )
   ex
 end
+
+"""
+    eltype(nlp::AbstractNLPModel{T, S})
+
+Element type of `nlp.meta.x0`.
+"""
+Base.eltype(nlp::AbstractNLPModel{T, S}) where {T, S} = eltype(nlp.meta.x0)

test/nlp/api.jl

@@ -7,6 +7,7 @@
   H(x, y) = H(x) + y[2] * [-0.5 0; 0 -2.0]
 
   nlp = SimpleNLPModel()
+  @test eltype(nlp) == Float64
   n = nlp.meta.nvar
   m = nlp.meta.ncon
 

test/nls/api.jl

@@ -4,6 +4,7 @@
   HF(x, w) = w[2] * [-20.0 0; 0 0]
 
   nls = SimpleNLSModel()
+  @test eltype(nls) == Float64
   n = nls.meta.nvar
   m = nls.meta.ncon
   ne = nls_meta(nls).nequ