InputOutputCurve function evaluation (#517)

* InputOutputCurve function evaluation

* put domain check inside function

Author: luke-kiernan

src/function_data.jl

@@ -652,8 +652,10 @@ _eval_fd_impl(
 "Evaluate the `PiecewiseLinearData` or `PiecewiseStepData` at a given x-coordinate"
 function (fd::Union{PiecewiseLinearData, PiecewiseStepData})(x::Real)
     lb, ub = get_domain(fd)
-    (x < lb || x > ub) &&
+    # defend against floating point precision issues at the boundaries.
+    ((lb <= x <= ub) || isapprox(x, lb) || isapprox(x, ub)) ||
         throw(ArgumentError("x=$x is outside the domain [$lb, $ub]"))
+    x = clamp(x, lb, ub)
     x_coords = get_x_coords(fd)
     y_coords = get_y_coords(fd)
     i_leq = searchsortedlast(x_coords, x)  # uses binary search!

src/value_curve.jl

@@ -41,6 +41,11 @@ InputOutputCurve{T}(
 ) where {(T <: Union{QuadraticFunctionData, LinearFunctionData, PiecewiseLinearData})} =
     InputOutputCurve{T}(function_data, nothing)
 
+"""
+Evaluate the `InputOutputCurve` at a given input value `x`.
+"""
+(ioc::InputOutputCurve)(x::Real) = get_function_data(ioc)(x)
+
 """
 An incremental (or 'marginal') curve, relating the production quantity to the derivative of
 cost: `y = f'(x)`. Can be used, for instance, in the representation of a [`CostCurve`](@ref)
@@ -62,7 +67,7 @@ IncrementalCurve(function_data, initial_input) =
 IncrementalCurve{T}(
     function_data,
     initial_input,
-) where {(T <: Union{QuadraticFunctionData, LinearFunctionData, PiecewiseLinearData})} =
+) where {(T <: Union{LinearFunctionData, PiecewiseStepData})} =
     IncrementalCurve{T}(function_data, initial_input, nothing)
 
 """
@@ -87,7 +92,7 @@ AverageRateCurve(function_data, initial_input) =
 AverageRateCurve{T}(
     function_data,
     initial_input,
-) where {(T <: Union{QuadraticFunctionData, LinearFunctionData, PiecewiseLinearData})} =
+) where {(T <: Union{LinearFunctionData, PiecewiseStepData})} =
     AverageRateCurve{T}(function_data, initial_input, nothing)
 
 "Get the `initial_input` field of this `ValueCurve` (not defined for `InputOutputCurve`)"

test/test_cost_functions.jl

@@ -337,3 +337,32 @@ end
     ) ==
           IS.LinearCurve(10.0, 7.0)
 end
+
+@testset "Test prohibited FunctionData types" begin
+    # Incremental and Average Rate curves only support
+    # linear and piecewise step function data.
+    q_fd = IS.QuadraticFunctionData(1, 2, 3)
+    pwl_fd = IS.PiecewiseLinearData([(x = 0.0, y = 1.0), (x = 1.0, y = 2.0)])
+    @test_throws MethodError IS.IncrementalCurve(q_fd, 0.0)
+    @test_throws MethodError IS.AverageRateCurve(q_fd, 0.0)
+    @test_throws MethodError IS.IncrementalCurve(pwl_fd, 0.0)
+    @test_throws MethodError IS.AverageRateCurve(pwl_fd, 0.0)
+end
+
+@testset "Test InputOutputCurve evaluation" begin
+    io_quadratic = IS.InputOutputCurve(IS.QuadraticFunctionData(1, 2, 3))
+    @test io_quadratic(0.0) == 3.0
+    @test io_quadratic(1.0) == 6.0
+    @test io_quadratic(2.0) == 11.0
+
+    io_linear = IS.InputOutputCurve(IS.LinearFunctionData(3, 2))
+    @test io_linear(0.0) == 2.0
+    @test io_linear(1.0) == 5.0
+    @test io_linear(2.0) == 8.0
+
+    pwl = IS.PiecewiseLinearData([(x = 1, y = 3), (x = 3, y = 7), (x = 5, y = 11)])
+    io_piecewise = IS.InputOutputCurve(pwl)
+    @test io_piecewise(1.0) == 3.0
+    @test io_piecewise(3.0) == 7.0
+    @test io_piecewise(5.0) == 11.0
+end

test/test_function_data.jl

@@ -689,3 +689,23 @@ end
               compact_plain_ans
     end
 end
+
+@testset "Test piecewise domain checking" begin
+    pwl = IS.PiecewiseStepData([1, 3, 5], [8, 10])
+
+    # floating point inputs
+    @test_throws ArgumentError pwl(0.5)
+    @test_throws ArgumentError pwl(5.5)
+    pwl(2.5)
+
+    # non floating point inputs
+    @test_throws ArgumentError pwl(1 // 2)
+    @test_throws ArgumentError pwl(5 + 1 // 2)
+    pwl(5 // 2)
+
+    # floating point precision edge cases (should not error)
+    @assert isapprox(1 - eps() / 2, 1)
+    @assert isapprox(5 + eps() / 2, 5)
+    pwl(1 - eps() / 2)
+    pwl(5 + eps() / 2)
+end