From 55dcc1d4bb9dd6368311e1dc9be3170ca8cfe0d5 Mon Sep 17 00:00:00 2001
From: Luke Kiernan <lkiernan@nrel.gov>
Date: Fri, 21 Nov 2025 14:12:35 -0700
Subject: [PATCH 1/2] InputOutputCurve function evaluation

---
 src/function_data.jl        | 19 ++++++++++++++++---
 src/value_curve.jl          |  9 +++++++--
 test/test_cost_functions.jl | 29 +++++++++++++++++++++++++++++
 test/test_function_data.jl  | 20 ++++++++++++++++++++
 4 files changed, 72 insertions(+), 5 deletions(-)

diff --git a/src/function_data.jl b/src/function_data.jl
index 172c163c2..60784ae50 100644
--- a/src/function_data.jl
+++ b/src/function_data.jl
@@ -649,11 +649,24 @@ _eval_fd_impl(
 ) =
     y_coords[i]
 
-"Evaluate the `PiecewiseLinearData` or `PiecewiseStepData` at a given x-coordinate"
-function (fd::Union{PiecewiseLinearData, PiecewiseStepData})(x::Real)
+function check_domain(fd::FunctionData, x::Real)
+    lb, ub = get_domain(fd)
+    (lb <= x <= ub) ||
+        throw(ArgumentError("x=$x is outside the domain [$lb, $ub]"))
+    return x
+end
+
+"Helper function to check domain with floating point tolerance."
+function check_domain(fd::FunctionData, x::AbstractFloat)
     lb, ub = get_domain(fd)
-    (x < lb || x > ub) &&
+    ((lb <= x <= ub) || isapprox(x, lb) || isapprox(x, ub)) ||
         throw(ArgumentError("x=$x is outside the domain [$lb, $ub]"))
+    return clamp(x, lb, ub)
+end
+
+"Evaluate the `PiecewiseLinearData` or `PiecewiseStepData` at a given x-coordinate"
+function (fd::Union{PiecewiseLinearData, PiecewiseStepData})(x::Real)
+    x = check_domain(fd, x)
     x_coords = get_x_coords(fd)
     y_coords = get_y_coords(fd)
     i_leq = searchsortedlast(x_coords, x)  # uses binary search!
diff --git a/src/value_curve.jl b/src/value_curve.jl
index 669cb6050..c9c221464 100644
--- a/src/value_curve.jl
+++ b/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`)"
diff --git a/test/test_cost_functions.jl b/test/test_cost_functions.jl
index 412337549..333a6a877 100644
--- a/test/test_cost_functions.jl
+++ b/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
diff --git a/test/test_function_data.jl b/test/test_function_data.jl
index 33b8b5a5c..fdb866553 100644
--- a/test/test_function_data.jl
+++ b/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

From 69859fd0666611233bc8dc5547e87ae83418b42b Mon Sep 17 00:00:00 2001
From: Luke Kiernan <lkiernan@nrel.gov>
Date: Fri, 21 Nov 2025 14:48:07 -0700
Subject: [PATCH 2/2] put domain check inside function

---
 src/function_data.jl | 19 ++++---------------
 1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/src/function_data.jl b/src/function_data.jl
index 60784ae50..94eecfd28 100644
--- a/src/function_data.jl
+++ b/src/function_data.jl
@@ -649,24 +649,13 @@ _eval_fd_impl(
 ) =
     y_coords[i]
 
-function check_domain(fd::FunctionData, x::Real)
-    lb, ub = get_domain(fd)
-    (lb <= x <= ub) ||
-        throw(ArgumentError("x=$x is outside the domain [$lb, $ub]"))
-    return x
-end
-
-"Helper function to check domain with floating point tolerance."
-function check_domain(fd::FunctionData, x::AbstractFloat)
+"Evaluate the `PiecewiseLinearData` or `PiecewiseStepData` at a given x-coordinate"
+function (fd::Union{PiecewiseLinearData, PiecewiseStepData})(x::Real)
     lb, ub = get_domain(fd)
+    # defend against floating point precision issues at the boundaries.
     ((lb <= x <= ub) || isapprox(x, lb) || isapprox(x, ub)) ||
         throw(ArgumentError("x=$x is outside the domain [$lb, $ub]"))
-    return clamp(x, lb, ub)
-end
-
-"Evaluate the `PiecewiseLinearData` or `PiecewiseStepData` at a given x-coordinate"
-function (fd::Union{PiecewiseLinearData, PiecewiseStepData})(x::Real)
-    x = check_domain(fd, x)
+    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!