refactor: move solver skeleton implementations to cpp

CMakeLists.txt

@@ -2,9 +2,11 @@ cmake_minimum_required(VERSION 3.20)
 
 project(FESA LANGUAGES CXX)
 
-add_library(fesa_core INTERFACE)
-target_compile_features(fesa_core INTERFACE cxx_std_17)
-target_include_directories(fesa_core INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/src)
+file(GLOB_RECURSE FESA_CORE_SOURCES CONFIGURE_DEPENDS src/fesa/*.cpp)
+
+add_library(fesa_core STATIC ${FESA_CORE_SOURCES})
+target_compile_features(fesa_core PUBLIC cxx_std_17)
+target_include_directories(fesa_core PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/src)
 
 enable_testing()
 add_subdirectory(tests)

docs/build-test-reports/solver-core-skeleton.md

@@ -7,12 +7,19 @@
 
 ## Commands Run
 
+```powershell
+python -m unittest scripts.test_header_declaration_only
+```
+
+- exit_code: 0
+- summary: Solver headers contain declarations only; function bodies are implemented in `.cpp` files.
+
 ```powershell
 python -m unittest discover -s scripts -p "test_*.py"
 ```
 
 - exit_code: 0
-- summary: 98 Python Harness tests passed.
+- summary: 99 Python Harness tests passed.
 
 ```powershell
 python scripts/validate_workspace.py
@@ -52,6 +59,15 @@ ctest --test-dir build/msvc-debug --output-on-failure -C Debug -R solver_core_sk
 - `results_containers_test`
 - `solver_core_skeleton_integration_test`
 
+## Structural Tests Added
+
+- `scripts.test_header_declaration_only`
+
+## Build Structure
+
+- `fesa_core` now builds as a static library from `src/fesa/**/*.cpp`.
+- Solver headers under `src/fesa/**/*.hpp` declare functions only; method bodies live in matching `.cpp` translation units.
+
 ## Known Limitations
 
 - No element stiffness, residual, tangent, or stress recovery calculation is implemented.

scripts/test_header_declaration_only.py

@@ -0,0 +1,45 @@
+import re
+import unittest
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+HEADER_ROOT = ROOT / "src" / "fesa"
+
+
+def _looks_like_function_definition(prefix):
+    if "(" not in prefix or ")" not in prefix:
+        return False
+
+    stripped = prefix.strip()
+    control_prefixes = ("if ", "for ", "while ", "switch ", "catch ")
+    declaration_prefixes = ("namespace ", "class ", "struct ", "enum ")
+    return not stripped.startswith(control_prefixes + declaration_prefixes)
+
+
+class HeaderDeclarationOnlyTests(unittest.TestCase):
+    def test_solver_headers_do_not_contain_function_bodies(self):
+        violations = []
+
+        for header in sorted(HEADER_ROOT.rglob("*.hpp")):
+            candidate = ""
+            for line_number, line in enumerate(header.read_text(encoding="utf-8").splitlines(), start=1):
+                stripped = line.strip()
+                if not stripped:
+                    continue
+
+                candidate = f"{candidate} {stripped}".strip()
+                if "{" in stripped and _looks_like_function_definition(candidate.split("{", 1)[0]):
+                    violations.append(f"{header.relative_to(ROOT)}:{line_number}: function body in header")
+
+                if re.search(r"\([^;{}]*\)\s*=\s*(default|delete)\s*;", stripped):
+                    violations.append(f"{header.relative_to(ROOT)}:{line_number}: function definition in header")
+
+                if stripped.endswith(";") or stripped.endswith("}") or stripped.endswith(":"):
+                    candidate = ""
+
+        self.assertEqual([], violations)
+
+
+if __name__ == "__main__":
+    unittest.main()

src/fesa/analysis/analysis.cpp

@@ -0,0 +1,30 @@
+#include <fesa/analysis/analysis.hpp>
+
+namespace fesa::analysis {
+
+Analysis::~Analysis() = default;
+
+void Analysis::run()
+{
+    initialize();
+    build_analysis_model();
+    build_dof_map();
+    build_sparse_pattern();
+    assemble();
+    apply_boundary_conditions();
+    solve();
+    update_state();
+    write_results();
+}
+
+void Analysis::initialize() {}
+void Analysis::build_analysis_model() {}
+void Analysis::build_dof_map() {}
+void Analysis::build_sparse_pattern() {}
+void Analysis::assemble() {}
+void Analysis::apply_boundary_conditions() {}
+void Analysis::solve() {}
+void Analysis::update_state() {}
+void Analysis::write_results() {}
+
+} // namespace fesa::analysis

src/fesa/analysis/analysis.hpp

@@ -4,31 +4,20 @@ namespace fesa::analysis {
 
 class Analysis {
 public:
-    virtual ~Analysis() = default;
+    virtual ~Analysis();
 
-    void run()
-    {
-        initialize();
-        build_analysis_model();
-        build_dof_map();
-        build_sparse_pattern();
-        assemble();
-        apply_boundary_conditions();
-        solve();
-        update_state();
-        write_results();
-    }
+    void run();
 
 protected:
-    virtual void initialize() {}
-    virtual void build_analysis_model() {}
-    virtual void build_dof_map() {}
-    virtual void build_sparse_pattern() {}
-    virtual void assemble() {}
-    virtual void apply_boundary_conditions() {}
-    virtual void solve() {}
-    virtual void update_state() {}
-    virtual void write_results() {}
+    virtual void initialize();
+    virtual void build_analysis_model();
+    virtual void build_dof_map();
+    virtual void build_sparse_pattern();
+    virtual void assemble();
+    virtual void apply_boundary_conditions();
+    virtual void solve();
+    virtual void update_state();
+    virtual void write_results();
 };
 
 } // namespace fesa::analysis

src/fesa/analysis/analysis_model.cpp

@@ -0,0 +1,60 @@
+#include <fesa/analysis/analysis_model.hpp>
+
+#include <stdexcept>
+
+namespace fesa::analysis {
+
+AnalysisModel::AnalysisModel(const model::Domain& domain, core::StepId step_id)
+    : domain_(domain), step_(domain.find_step(step_id))
+{
+    if (step_ == nullptr) {
+        throw std::invalid_argument("analysis step not found");
+    }
+
+    for (const auto& element : domain_.elements()) {
+        active_elements_.push_back(&element);
+    }
+    for (const auto& boundary_condition : step_->boundary_conditions()) {
+        active_boundary_conditions_.push_back(&boundary_condition);
+    }
+    for (const auto& load : step_->loads()) {
+        active_loads_.push_back(&load);
+    }
+}
+
+const model::Domain& AnalysisModel::domain() const
+{
+    return domain_;
+}
+
+const model::AnalysisStep& AnalysisModel::step() const
+{
+    return *step_;
+}
+
+const std::vector<const model::Element*>& AnalysisModel::active_elements() const
+{
+    return active_elements_;
+}
+
+const std::vector<const model::BoundaryCondition*>& AnalysisModel::active_boundary_conditions() const
+{
+    return active_boundary_conditions_;
+}
+
+const std::vector<const model::Load*>& AnalysisModel::active_loads() const
+{
+    return active_loads_;
+}
+
+const model::Property* AnalysisModel::property_for(const model::Element& element) const
+{
+    return domain_.find_property(element.property_id());
+}
+
+const model::Material* AnalysisModel::material_for(const model::Property& property) const
+{
+    return domain_.find_material(property.material_id());
+}
+
+} // namespace fesa::analysis

src/fesa/analysis/analysis_model.hpp

@@ -2,65 +2,21 @@
 
 #include <fesa/model/domain.hpp>
 
-#include <stdexcept>
 #include <vector>
 
 namespace fesa::analysis {
 
 class AnalysisModel {
 public:
-    AnalysisModel(const model::Domain& domain, core::StepId step_id)
-        : domain_(domain), step_(domain.find_step(step_id))
-    {
-        if (step_ == nullptr) {
-            throw std::invalid_argument("analysis step not found");
-        }
+    AnalysisModel(const model::Domain& domain, core::StepId step_id);
 
-        for (const auto& element : domain_.elements()) {
-            active_elements_.push_back(&element);
-        }
-        for (const auto& boundary_condition : step_->boundary_conditions()) {
-            active_boundary_conditions_.push_back(&boundary_condition);
-        }
-        for (const auto& load : step_->loads()) {
-            active_loads_.push_back(&load);
-        }
-    }
-
-    const model::Domain& domain() const
-    {
-        return domain_;
-    }
-
-    const model::AnalysisStep& step() const
-    {
-        return *step_;
-    }
-
-    const std::vector<const model::Element*>& active_elements() const
-    {
-        return active_elements_;
-    }
-
-    const std::vector<const model::BoundaryCondition*>& active_boundary_conditions() const
-    {
-        return active_boundary_conditions_;
-    }
-
-    const std::vector<const model::Load*>& active_loads() const
-    {
-        return active_loads_;
-    }
-
-    const model::Property* property_for(const model::Element& element) const
-    {
-        return domain_.find_property(element.property_id());
-    }
-
-    const model::Material* material_for(const model::Property& property) const
-    {
-        return domain_.find_material(property.material_id());
-    }
+    const model::Domain& domain() const;
+    const model::AnalysisStep& step() const;
+    const std::vector<const model::Element*>& active_elements() const;
+    const std::vector<const model::BoundaryCondition*>& active_boundary_conditions() const;
+    const std::vector<const model::Load*>& active_loads() const;
+    const model::Property* property_for(const model::Element& element) const;
+    const model::Material* material_for(const model::Property& property) const;
 
 private:
     const model::Domain& domain_;

src/fesa/analysis/analysis_state.cpp

@@ -0,0 +1,124 @@
+#include <fesa/analysis/analysis_state.hpp>
+
+#include <cstddef>
+#include <stdexcept>
+#include <utility>
+
+namespace fesa::analysis {
+
+AnalysisState::AnalysisState(int total_dof_count)
+    : displacement_(vector_of(total_dof_count)),
+      velocity_(vector_of(total_dof_count)),
+      acceleration_(vector_of(total_dof_count)),
+      temperature_(vector_of(total_dof_count)),
+      external_force_(vector_of(total_dof_count)),
+      internal_force_(vector_of(total_dof_count)),
+      residual_(vector_of(total_dof_count))
+{
+}
+
+const std::vector<double>& AnalysisState::displacement() const
+{
+    return displacement_;
+}
+
+const std::vector<double>& AnalysisState::velocity() const
+{
+    return velocity_;
+}
+
+const std::vector<double>& AnalysisState::acceleration() const
+{
+    return acceleration_;
+}
+
+const std::vector<double>& AnalysisState::temperature() const
+{
+    return temperature_;
+}
+
+const std::vector<double>& AnalysisState::external_force() const
+{
+    return external_force_;
+}
+
+const std::vector<double>& AnalysisState::internal_force() const
+{
+    return internal_force_;
+}
+
+const std::vector<double>& AnalysisState::residual() const
+{
+    return residual_;
+}
+
+void AnalysisState::set_displacement(std::vector<double> values)
+{
+    assign_same_size(displacement_, std::move(values));
+}
+
+void AnalysisState::set_external_force(std::vector<double> values)
+{
+    assign_same_size(external_force_, std::move(values));
+}
+
+void AnalysisState::set_internal_force(std::vector<double> values)
+{
+    assign_same_size(internal_force_, std::move(values));
+}
+
+void AnalysisState::update_residual()
+{
+    for (std::size_t index = 0; index < residual_.size(); ++index) {
+        residual_[index] = external_force_[index] - internal_force_[index];
+    }
+}
+
+IterationState& AnalysisState::iteration_state()
+{
+    return iteration_state_;
+}
+
+const IterationState& AnalysisState::iteration_state() const
+{
+    return iteration_state_;
+}
+
+void AnalysisState::set_element_state(core::ElementId element_id, std::vector<double> state)
+{
+    for (auto& entry : element_states_) {
+        if (entry.first.value == element_id.value) {
+            entry.second = std::move(state);
+            return;
+        }
+    }
+    element_states_.push_back({element_id, std::move(state)});
+}
+
+const std::vector<double>* AnalysisState::element_state(core::ElementId element_id) const
+{
+    for (const auto& entry : element_states_) {
+        if (entry.first.value == element_id.value) {
+            return &entry.second;
+        }
+    }
+    return nullptr;
+}
+
+std::vector<double> AnalysisState::vector_of(int size)
+{
+    if (size < 0) {
+        throw std::invalid_argument("negative dof count");
+    }
+    return std::vector<double>(static_cast<std::size_t>(size), 0.0);
+}
+
+void AnalysisState::assign_same_size(std::vector<double>& target, std::vector<double> values)
+{
+    if (target.size() != values.size()) {
+        throw std::invalid_argument("vector size mismatch");
+    }
+    target = std::move(values);
+}
+
+} // namespace fesa::analysis

src/fesa/analysis/analysis_state.hpp

@@ -2,8 +2,6 @@
 
 #include <fesa/core/ids.hpp>
 
-#include <stdexcept>
-#include <utility>
 #include <vector>
 
 namespace fesa::analysis {
@@ -16,121 +14,30 @@ struct IterationState {
 
 class AnalysisState {
 public:
-    explicit AnalysisState(int total_dof_count)
-        : displacement_(vector_of(total_dof_count)),
-          velocity_(vector_of(total_dof_count)),
-          acceleration_(vector_of(total_dof_count)),
-          temperature_(vector_of(total_dof_count)),
-          external_force_(vector_of(total_dof_count)),
-          internal_force_(vector_of(total_dof_count)),
-          residual_(vector_of(total_dof_count))
-    {
-    }
+    explicit AnalysisState(int total_dof_count);
 
-    const std::vector<double>& displacement() const
-    {
-        return displacement_;
-    }
+    const std::vector<double>& displacement() const;
+    const std::vector<double>& velocity() const;
+    const std::vector<double>& acceleration() const;
+    const std::vector<double>& temperature() const;
+    const std::vector<double>& external_force() const;
+    const std::vector<double>& internal_force() const;
+    const std::vector<double>& residual() const;
 
-    const std::vector<double>& velocity() const
-    {
-        return velocity_;
-    }
+    void set_displacement(std::vector<double> values);
+    void set_external_force(std::vector<double> values);
+    void set_internal_force(std::vector<double> values);
+    void update_residual();
 
-    const std::vector<double>& acceleration() const
-    {
-        return acceleration_;
-    }
+    IterationState& iteration_state();
+    const IterationState& iteration_state() const;
 
-    const std::vector<double>& temperature() const
-    {
-        return temperature_;
-    }
-
-    const std::vector<double>& external_force() const
-    {
-        return external_force_;
-    }
-
-    const std::vector<double>& internal_force() const
-    {
-        return internal_force_;
-    }
-
-    const std::vector<double>& residual() const
-    {
-        return residual_;
-    }
-
-    void set_displacement(std::vector<double> values)
-    {
-        assign_same_size(displacement_, std::move(values));
-    }
-
-    void set_external_force(std::vector<double> values)
-    {
-        assign_same_size(external_force_, std::move(values));
-    }
-
-    void set_internal_force(std::vector<double> values)
-    {
-        assign_same_size(internal_force_, std::move(values));
-    }
-
-    void update_residual()
-    {
-        for (std::size_t index = 0; index < residual_.size(); ++index) {
-            residual_[index] = external_force_[index] - internal_force_[index];
-        }
-    }
-
-    IterationState& iteration_state()
-    {
-        return iteration_state_;
-    }
-
-    const IterationState& iteration_state() const
-    {
-        return iteration_state_;
-    }
-
-    void set_element_state(core::ElementId element_id, std::vector<double> state)
-    {
-        for (auto& entry : element_states_) {
-            if (entry.first.value == element_id.value) {
-                entry.second = std::move(state);
-                return;
-            }
-        }
-        element_states_.push_back({element_id, std::move(state)});
-    }
-
-    const std::vector<double>* element_state(core::ElementId element_id) const
-    {
-        for (const auto& entry : element_states_) {
-            if (entry.first.value == element_id.value) {
-                return &entry.second;
-            }
-        }
-        return nullptr;
-    }
+    void set_element_state(core::ElementId element_id, std::vector<double> state);
+    const std::vector<double>* element_state(core::ElementId element_id) const;
 
 private:
-    static std::vector<double> vector_of(int size)
-    {
-        if (size < 0) {
-            throw std::invalid_argument("negative dof count");
-        }
-        return std::vector<double>(static_cast<std::size_t>(size), 0.0);
-    }
-
-    static void assign_same_size(std::vector<double>& target, std::vector<double> values)
-    {
-        if (target.size() != values.size()) {
-            throw std::invalid_argument("vector size mismatch");
-        }
-        target = std::move(values);
-    }
+    static std::vector<double> vector_of(int size);
+    static void assign_same_size(std::vector<double>& target, std::vector<double> values);
 
     std::vector<double> displacement_;
     std::vector<double> velocity_;

src/fesa/analysis/linear_static_analysis.cpp

@@ -0,0 +1,48 @@
+#include <fesa/analysis/linear_static_analysis.hpp>
+
+namespace fesa::analysis {
+
+LinearStaticAnalysis::LinearStaticAnalysis(const model::Domain& domain, core::StepId step_id)
+    : domain_(domain), step_id_(step_id)
+{
+}
+
+const AnalysisModel* LinearStaticAnalysis::analysis_model() const
+{
+    return analysis_model_.get();
+}
+
+const AnalysisState* LinearStaticAnalysis::state() const
+{
+    return state_.get();
+}
+
+void LinearStaticAnalysis::build_analysis_model()
+{
+    analysis_model_ = std::make_unique<AnalysisModel>(domain_, step_id_);
+}
+
+void LinearStaticAnalysis::build_dof_map()
+{
+    dof_manager_ = std::make_unique<fem::DofManager>();
+    for (const auto* element : analysis_model_->active_elements()) {
+        for (const auto node_id : element->node_ids()) {
+            dof_manager_->define_node_dofs(node_id, {
+                model::DofComponent::ux,
+                model::DofComponent::uy,
+                model::DofComponent::uz
+            });
+        }
+    }
+    for (const auto* boundary_condition : analysis_model_->active_boundary_conditions()) {
+        dof_manager_->apply_boundary_condition(*boundary_condition);
+    }
+    dof_manager_->number_equations();
+}
+
+void LinearStaticAnalysis::update_state()
+{
+    state_ = std::make_unique<AnalysisState>(dof_manager_->total_dof_count());
+}
+
+} // namespace fesa::analysis

src/fesa/analysis/linear_static_analysis.hpp

@@ -11,49 +11,15 @@ namespace fesa::analysis {
 
 class LinearStaticAnalysis : public Analysis {
 public:
-    LinearStaticAnalysis(const model::Domain& domain, core::StepId step_id)
-        : domain_(domain), step_id_(step_id)
-    {
-    }
+    LinearStaticAnalysis(const model::Domain& domain, core::StepId step_id);
 
-    const AnalysisModel* analysis_model() const
-    {
-        return analysis_model_.get();
-    }
-
-    const AnalysisState* state() const
-    {
-        return state_.get();
-    }
+    const AnalysisModel* analysis_model() const;
+    const AnalysisState* state() const;
 
 protected:
-    void build_analysis_model() override
-    {
-        analysis_model_ = std::make_unique<AnalysisModel>(domain_, step_id_);
-    }
-
-    void build_dof_map() override
-    {
-        dof_manager_ = std::make_unique<fem::DofManager>();
-        for (const auto* element : analysis_model_->active_elements()) {
-            for (const auto node_id : element->node_ids()) {
-                dof_manager_->define_node_dofs(node_id, {
-                    model::DofComponent::ux,
-                    model::DofComponent::uy,
-                    model::DofComponent::uz
-                });
-            }
-        }
-        for (const auto* boundary_condition : analysis_model_->active_boundary_conditions()) {
-            dof_manager_->apply_boundary_condition(*boundary_condition);
-        }
-        dof_manager_->number_equations();
-    }
-
-    void update_state() override
-    {
-        state_ = std::make_unique<AnalysisState>(dof_manager_->total_dof_count());
-    }
+    void build_analysis_model() override;
+    void build_dof_map() override;
+    void update_state() override;
 
 private:
     const model::Domain& domain_;

src/fesa/core/status.cpp

@@ -0,0 +1,34 @@
+#include <fesa/core/status.hpp>
+
+#include <utility>
+
+namespace fesa::core {
+
+Status Status::ok()
+{
+    return Status{};
+}
+
+Status Status::failure(Diagnostic diagnostic)
+{
+    Status status;
+    status.add(std::move(diagnostic));
+    return status;
+}
+
+bool Status::is_ok() const
+{
+    return diagnostics_.empty();
+}
+
+const std::vector<Diagnostic>& Status::diagnostics() const
+{
+    return diagnostics_;
+}
+
+void Status::add(Diagnostic diagnostic)
+{
+    diagnostics_.push_back(std::move(diagnostic));
+}
+
+} // namespace fesa::core

src/fesa/core/status.hpp

@@ -2,39 +2,18 @@
 
 #include <fesa/core/diagnostic.hpp>
 
-#include <utility>
 #include <vector>
 
 namespace fesa::core {
 
 class Status {
 public:
-    static Status ok()
-    {
-        return Status{};
-    }
+    static Status ok();
+    static Status failure(Diagnostic diagnostic);
 
-    static Status failure(Diagnostic diagnostic)
-    {
-        Status status;
-        status.add(std::move(diagnostic));
-        return status;
-    }
-
-    bool is_ok() const
-    {
-        return diagnostics_.empty();
-    }
-
-    const std::vector<Diagnostic>& diagnostics() const
-    {
-        return diagnostics_;
-    }
-
-    void add(Diagnostic diagnostic)
-    {
-        diagnostics_.push_back(std::move(diagnostic));
-    }
+    bool is_ok() const;
+    const std::vector<Diagnostic>& diagnostics() const;
+    void add(Diagnostic diagnostic);
 
 private:
     std::vector<Diagnostic> diagnostics_;

src/fesa/fem/dof_key.cpp

@@ -0,0 +1,10 @@
+#include <fesa/fem/dof_key.hpp>
+
+namespace fesa::fem {
+
+bool operator==(const DofKey& lhs, const DofKey& rhs)
+{
+    return lhs.node_id.value == rhs.node_id.value && lhs.component == rhs.component;
+}
+
+} // namespace fesa::fem

src/fesa/fem/dof_key.hpp

@@ -10,9 +10,6 @@ struct DofKey {
     model::DofComponent component;
 };
 
-inline bool operator==(const DofKey& lhs, const DofKey& rhs)
-{
-    return lhs.node_id.value == rhs.node_id.value && lhs.component == rhs.component;
-}
+bool operator==(const DofKey& lhs, const DofKey& rhs);
 
 } // namespace fesa::fem

src/fesa/fem/dof_manager.cpp

@@ -0,0 +1,133 @@
+#include <fesa/fem/dof_manager.hpp>
+
+#include <algorithm>
+#include <cstddef>
+#include <stdexcept>
+
+namespace fesa::fem {
+
+void DofManager::define_node_dofs(core::NodeId node_id, std::vector<model::DofComponent> components)
+{
+    for (const auto component : components) {
+        DofKey key{node_id, component};
+        if (find_record(key) == records_.end()) {
+            records_.push_back({key});
+        }
+    }
+}
+
+void DofManager::apply_boundary_condition(const model::BoundaryCondition& bc)
+{
+    auto record = find_record({bc.node_id(), bc.component()});
+    if (record == records_.end()) {
+        throw std::invalid_argument("boundary condition references undefined dof");
+    }
+    record->constrained = true;
+}
+
+void DofManager::number_equations()
+{
+    std::sort(records_.begin(), records_.end(), [](const Record& lhs, const Record& rhs) {
+        if (lhs.key.node_id.value != rhs.key.node_id.value) {
+            return lhs.key.node_id.value < rhs.key.node_id.value;
+        }
+        return static_cast<int>(lhs.key.component) < static_cast<int>(rhs.key.component);
+    });
+
+    int free_id = 0;
+    for (int equation_id = 0; equation_id < static_cast<int>(records_.size()); ++equation_id) {
+        records_[equation_id].equation_id = equation_id;
+        if (records_[equation_id].constrained) {
+            records_[equation_id].free_equation_id = std::nullopt;
+        } else {
+            records_[equation_id].free_equation_id = free_id++;
+        }
+    }
+
+    sparse_pattern_.clear();
+    for (int row = 0; row < free_id; ++row) {
+        for (int column = 0; column < free_id; ++column) {
+            sparse_pattern_.push_back({row, column});
+        }
+    }
+}
+
+int DofManager::total_dof_count() const
+{
+    return static_cast<int>(records_.size());
+}
+
+int DofManager::free_dof_count() const
+{
+    return static_cast<int>(
+        std::count_if(records_.begin(), records_.end(), [](const Record& record) {
+            return !record.constrained;
+        })
+    );
+}
+
+int DofManager::constrained_dof_count() const
+{
+    return total_dof_count() - free_dof_count();
+}
+
+bool DofManager::is_constrained(DofKey key) const
+{
+    return require_record(key).constrained;
+}
+
+int DofManager::equation_id(DofKey key) const
+{
+    return require_record(key).equation_id;
+}
+
+std::optional<int> DofManager::free_equation_id(DofKey key) const
+{
+    return require_record(key).free_equation_id;
+}
+
+std::vector<double> DofManager::expand_free_vector(const std::vector<double>& free_values) const
+{
+    if (free_values.size() != static_cast<std::size_t>(free_dof_count())) {
+        throw std::invalid_argument("free vector size does not match dof manager");
+    }
+
+    std::vector<double> full(records_.size(), 0.0);
+    for (const auto& record : records_) {
+        if (record.free_equation_id.has_value()) {
+            full[static_cast<std::size_t>(record.equation_id)] =
+                free_values[static_cast<std::size_t>(*record.free_equation_id)];
+        }
+    }
+    return full;
+}
+
+const std::vector<std::pair<int, int>>& DofManager::sparse_pattern() const
+{
+    return sparse_pattern_;
+}
+
+std::vector<DofManager::Record>::iterator DofManager::find_record(DofKey key)
+{
+    return std::find_if(records_.begin(), records_.end(), [key](const Record& record) {
+        return record.key == key;
+    });
+}
+
+std::vector<DofManager::Record>::const_iterator DofManager::find_record(DofKey key) const
+{
+    return std::find_if(records_.begin(), records_.end(), [key](const Record& record) {
+        return record.key == key;
+    });
+}
+
+const DofManager::Record& DofManager::require_record(DofKey key) const
+{
+    const auto record = find_record(key);
+    if (record == records_.end()) {
+        throw std::invalid_argument("dof is not defined");
+    }
+    return *record;
+}
+
+} // namespace fesa::fem

src/fesa/fem/dof_manager.hpp

@@ -2,9 +2,7 @@
 
 #include <fesa/fem/dof_key.hpp>
 
-#include <algorithm>
 #include <optional>
-#include <stdexcept>
 #include <utility>
 #include <vector>
 
@@ -12,106 +10,18 @@ namespace fesa::fem {
 
 class DofManager {
 public:
-    void define_node_dofs(core::NodeId node_id, std::vector<model::DofComponent> components)
-    {
-        for (const auto component : components) {
-            DofKey key{node_id, component};
-            if (find_record(key) == records_.end()) {
-                records_.push_back({key});
-            }
-        }
-    }
+    void define_node_dofs(core::NodeId node_id, std::vector<model::DofComponent> components);
+    void apply_boundary_condition(const model::BoundaryCondition& bc);
+    void number_equations();
 
-    void apply_boundary_condition(const model::BoundaryCondition& bc)
-    {
-        auto record = find_record({bc.node_id(), bc.component()});
-        if (record == records_.end()) {
-            throw std::invalid_argument("boundary condition references undefined dof");
-        }
-        record->constrained = true;
-    }
-
-    void number_equations()
-    {
-        std::sort(records_.begin(), records_.end(), [](const Record& lhs, const Record& rhs) {
-            if (lhs.key.node_id.value != rhs.key.node_id.value) {
-                return lhs.key.node_id.value < rhs.key.node_id.value;
-            }
-            return static_cast<int>(lhs.key.component) < static_cast<int>(rhs.key.component);
-        });
-
-        int free_id = 0;
-        for (int equation_id = 0; equation_id < static_cast<int>(records_.size()); ++equation_id) {
-            records_[equation_id].equation_id = equation_id;
-            if (records_[equation_id].constrained) {
-                records_[equation_id].free_equation_id = std::nullopt;
-            } else {
-                records_[equation_id].free_equation_id = free_id++;
-            }
-        }
-
-        sparse_pattern_.clear();
-        for (int row = 0; row < free_id; ++row) {
-            for (int column = 0; column < free_id; ++column) {
-                sparse_pattern_.push_back({row, column});
-            }
-        }
-    }
-
-    int total_dof_count() const
-    {
-        return static_cast<int>(records_.size());
-    }
-
-    int free_dof_count() const
-    {
-        return static_cast<int>(
-            std::count_if(records_.begin(), records_.end(), [](const Record& record) {
-                return !record.constrained;
-            })
-        );
-    }
-
-    int constrained_dof_count() const
-    {
-        return total_dof_count() - free_dof_count();
-    }
-
-    bool is_constrained(DofKey key) const
-    {
-        return require_record(key).constrained;
-    }
-
-    int equation_id(DofKey key) const
-    {
-        return require_record(key).equation_id;
-    }
-
-    std::optional<int> free_equation_id(DofKey key) const
-    {
-        return require_record(key).free_equation_id;
-    }
-
-    std::vector<double> expand_free_vector(const std::vector<double>& free_values) const
-    {
-        if (free_values.size() != static_cast<std::size_t>(free_dof_count())) {
-            throw std::invalid_argument("free vector size does not match dof manager");
-        }
-
-        std::vector<double> full(records_.size(), 0.0);
-        for (const auto& record : records_) {
-            if (record.free_equation_id.has_value()) {
-                full[static_cast<std::size_t>(record.equation_id)] =
-                    free_values[static_cast<std::size_t>(*record.free_equation_id)];
-            }
-        }
-        return full;
-    }
-
-    const std::vector<std::pair<int, int>>& sparse_pattern() const
-    {
-        return sparse_pattern_;
-    }
+    int total_dof_count() const;
+    int free_dof_count() const;
+    int constrained_dof_count() const;
+    bool is_constrained(DofKey key) const;
+    int equation_id(DofKey key) const;
+    std::optional<int> free_equation_id(DofKey key) const;
+    std::vector<double> expand_free_vector(const std::vector<double>& free_values) const;
+    const std::vector<std::pair<int, int>>& sparse_pattern() const;
 
 private:
     struct Record {
@@ -121,28 +31,9 @@ private:
         std::optional<int> free_equation_id;
     };
 
-    std::vector<Record>::iterator find_record(DofKey key)
-    {
-        return std::find_if(records_.begin(), records_.end(), [key](const Record& record) {
-            return record.key == key;
-        });
-    }
-
-    std::vector<Record>::const_iterator find_record(DofKey key) const
-    {
-        return std::find_if(records_.begin(), records_.end(), [key](const Record& record) {
-            return record.key == key;
-        });
-    }
-
-    const Record& require_record(DofKey key) const
-    {
-        const auto record = find_record(key);
-        if (record == records_.end()) {
-            throw std::invalid_argument("dof is not defined");
-        }
-        return *record;
-    }
+    std::vector<Record>::iterator find_record(DofKey key);
+    std::vector<Record>::const_iterator find_record(DofKey key) const;
+    const Record& require_record(DofKey key) const;
 
     std::vector<Record> records_;
     std::vector<std::pair<int, int>> sparse_pattern_;

src/fesa/model/analysis_step.cpp

@@ -0,0 +1,42 @@
+#include <fesa/model/analysis_step.hpp>
+
+#include <utility>
+
+namespace fesa::model {
+
+AnalysisStep::AnalysisStep(core::StepId id, std::string name)
+    : id_(id), name_(std::move(name))
+{
+}
+
+core::StepId AnalysisStep::id() const
+{
+    return id_;
+}
+
+const std::string& AnalysisStep::name() const
+{
+    return name_;
+}
+
+void AnalysisStep::add_boundary_condition(BoundaryCondition bc)
+{
+    boundary_conditions_.push_back(std::move(bc));
+}
+
+void AnalysisStep::add_load(Load load)
+{
+    loads_.push_back(std::move(load));
+}
+
+const std::vector<BoundaryCondition>& AnalysisStep::boundary_conditions() const
+{
+    return boundary_conditions_;
+}
+
+const std::vector<Load>& AnalysisStep::loads() const
+{
+    return loads_;
+}
+
+} // namespace fesa::model

src/fesa/model/analysis_step.hpp

@@ -4,47 +4,20 @@
 #include <fesa/model/load.hpp>
 
 #include <string>
-#include <utility>
 #include <vector>
 
 namespace fesa::model {
 
 class AnalysisStep {
 public:
-    AnalysisStep(core::StepId id, std::string name)
-        : id_(id), name_(std::move(name))
-    {
-    }
+    AnalysisStep(core::StepId id, std::string name);
 
-    core::StepId id() const
-    {
-        return id_;
-    }
-
-    const std::string& name() const
-    {
-        return name_;
-    }
-
-    void add_boundary_condition(BoundaryCondition bc)
-    {
-        boundary_conditions_.push_back(std::move(bc));
-    }
-
-    void add_load(Load load)
-    {
-        loads_.push_back(std::move(load));
-    }
-
-    const std::vector<BoundaryCondition>& boundary_conditions() const
-    {
-        return boundary_conditions_;
-    }
-
-    const std::vector<Load>& loads() const
-    {
-        return loads_;
-    }
+    core::StepId id() const;
+    const std::string& name() const;
+    void add_boundary_condition(BoundaryCondition bc);
+    void add_load(Load load);
+    const std::vector<BoundaryCondition>& boundary_conditions() const;
+    const std::vector<Load>& loads() const;
 
 private:
     core::StepId id_;

src/fesa/model/boundary_condition.cpp

@@ -0,0 +1,25 @@
+#include <fesa/model/boundary_condition.hpp>
+
+namespace fesa::model {
+
+BoundaryCondition::BoundaryCondition(core::NodeId node_id, DofComponent component, double value)
+    : node_id_(node_id), component_(component), value_(value)
+{
+}
+
+core::NodeId BoundaryCondition::node_id() const
+{
+    return node_id_;
+}
+
+DofComponent BoundaryCondition::component() const
+{
+    return component_;
+}
+
+double BoundaryCondition::value() const
+{
+    return value_;
+}
+
+} // namespace fesa::model

src/fesa/model/boundary_condition.hpp

@@ -16,25 +16,11 @@ enum class DofComponent {
 
 class BoundaryCondition {
 public:
-    BoundaryCondition(core::NodeId node_id, DofComponent component, double value)
-        : node_id_(node_id), component_(component), value_(value)
-    {
-    }
+    BoundaryCondition(core::NodeId node_id, DofComponent component, double value);
 
-    core::NodeId node_id() const
-    {
-        return node_id_;
-    }
-
-    DofComponent component() const
-    {
-        return component_;
-    }
-
-    double value() const
-    {
-        return value_;
-    }
+    core::NodeId node_id() const;
+    DofComponent component() const;
+    double value() const;
 
 private:
     core::NodeId node_id_;

src/fesa/model/domain.cpp

@@ -0,0 +1,107 @@
+#include <fesa/model/domain.hpp>
+
+#include <utility>
+
+namespace fesa::model {
+
+void Domain::add_node(Node node)
+{
+    nodes_.push_back(std::move(node));
+}
+
+void Domain::add_element(Element element)
+{
+    elements_.push_back(std::move(element));
+}
+
+void Domain::add_material(Material material)
+{
+    materials_.push_back(std::move(material));
+}
+
+void Domain::add_property(Property property)
+{
+    properties_.push_back(std::move(property));
+}
+
+void Domain::add_step(AnalysisStep step)
+{
+    steps_.push_back(std::move(step));
+}
+
+const std::vector<Node>& Domain::nodes() const
+{
+    return nodes_;
+}
+
+const std::vector<Element>& Domain::elements() const
+{
+    return elements_;
+}
+
+const std::vector<Material>& Domain::materials() const
+{
+    return materials_;
+}
+
+const std::vector<Property>& Domain::properties() const
+{
+    return properties_;
+}
+
+const std::vector<AnalysisStep>& Domain::steps() const
+{
+    return steps_;
+}
+
+const Node* Domain::find_node(core::NodeId id) const
+{
+    for (const auto& node : nodes_) {
+        if (node.id().value == id.value) {
+            return &node;
+        }
+    }
+    return nullptr;
+}
+
+const Element* Domain::find_element(core::ElementId id) const
+{
+    for (const auto& element : elements_) {
+        if (element.id().value == id.value) {
+            return &element;
+        }
+    }
+    return nullptr;
+}
+
+const Material* Domain::find_material(core::MaterialId id) const
+{
+    for (const auto& material : materials_) {
+        if (material.id().value == id.value) {
+            return &material;
+        }
+    }
+    return nullptr;
+}
+
+const Property* Domain::find_property(core::PropertyId id) const
+{
+    for (const auto& property : properties_) {
+        if (property.id().value == id.value) {
+            return &property;
+        }
+    }
+    return nullptr;
+}
+
+const AnalysisStep* Domain::find_step(core::StepId id) const
+{
+    for (const auto& step : steps_) {
+        if (step.id().value == id.value) {
+            return &step;
+        }
+    }
+    return nullptr;
+}
+
+} // namespace fesa::model

src/fesa/model/domain.hpp

@@ -6,112 +6,29 @@
 #include <fesa/model/node.hpp>
 #include <fesa/model/property.hpp>
 
-#include <utility>
 #include <vector>
 
 namespace fesa::model {
 
 class Domain {
 public:
-    void add_node(Node node)
-    {
-        nodes_.push_back(std::move(node));
-    }
+    void add_node(Node node);
+    void add_element(Element element);
+    void add_material(Material material);
+    void add_property(Property property);
+    void add_step(AnalysisStep step);
 
-    void add_element(Element element)
-    {
-        elements_.push_back(std::move(element));
-    }
+    const std::vector<Node>& nodes() const;
+    const std::vector<Element>& elements() const;
+    const std::vector<Material>& materials() const;
+    const std::vector<Property>& properties() const;
+    const std::vector<AnalysisStep>& steps() const;
 
-    void add_material(Material material)
-    {
-        materials_.push_back(std::move(material));
-    }
-
-    void add_property(Property property)
-    {
-        properties_.push_back(std::move(property));
-    }
-
-    void add_step(AnalysisStep step)
-    {
-        steps_.push_back(std::move(step));
-    }
-
-    const std::vector<Node>& nodes() const
-    {
-        return nodes_;
-    }
-
-    const std::vector<Element>& elements() const
-    {
-        return elements_;
-    }
-
-    const std::vector<Material>& materials() const
-    {
-        return materials_;
-    }
-
-    const std::vector<Property>& properties() const
-    {
-        return properties_;
-    }
-
-    const std::vector<AnalysisStep>& steps() const
-    {
-        return steps_;
-    }
-
-    const Node* find_node(core::NodeId id) const
-    {
-        for (const auto& node : nodes_) {
-            if (node.id().value == id.value) {
-                return &node;
-            }
-        }
-        return nullptr;
-    }
-
-    const Element* find_element(core::ElementId id) const
-    {
-        for (const auto& element : elements_) {
-            if (element.id().value == id.value) {
-                return &element;
-            }
-        }
-        return nullptr;
-    }
-
-    const Material* find_material(core::MaterialId id) const
-    {
-        for (const auto& material : materials_) {
-            if (material.id().value == id.value) {
-                return &material;
-            }
-        }
-        return nullptr;
-    }
-
-    const Property* find_property(core::PropertyId id) const
-    {
-        for (const auto& property : properties_) {
-            if (property.id().value == id.value) {
-                return &property;
-            }
-        }
-        return nullptr;
-    }
-
-    const AnalysisStep* find_step(core::StepId id) const
-    {
-        for (const auto& step : steps_) {
-            if (step.id().value == id.value) {
-                return &step;
-            }
-        }
-        return nullptr;
-    }
+    const Node* find_node(core::NodeId id) const;
+    const Element* find_element(core::ElementId id) const;
+    const Material* find_material(core::MaterialId id) const;
+    const Property* find_property(core::PropertyId id) const;
+    const AnalysisStep* find_step(core::StepId id) const;
 
 private:
     std::vector<Node> nodes_;

src/fesa/model/element.cpp

@@ -0,0 +1,38 @@
+#include <fesa/model/element.hpp>
+
+#include <utility>
+
+namespace fesa::model {
+
+Element::Element(core::ElementId id,
+                 ElementTopology topology,
+                 std::vector<core::NodeId> node_ids,
+                 core::PropertyId property_id)
+    : id_(id),
+      topology_(topology),
+      node_ids_(std::move(node_ids)),
+      property_id_(property_id)
+{
+}
+
+core::ElementId Element::id() const
+{
+    return id_;
+}
+
+ElementTopology Element::topology() const
+{
+    return topology_;
+}
+
+const std::vector<core::NodeId>& Element::node_ids() const
+{
+    return node_ids_;
+}
+
+core::PropertyId Element::property_id() const
+{
+    return property_id_;
+}
+
+} // namespace fesa::model

src/fesa/model/element.hpp

@@ -2,7 +2,6 @@
 
 #include <fesa/core/ids.hpp>
 
-#include <utility>
 #include <vector>
 
 namespace fesa::model {
@@ -18,33 +17,12 @@ public:
     Element(core::ElementId id,
             ElementTopology topology,
             std::vector<core::NodeId> node_ids,
-            core::PropertyId property_id)
-        : id_(id),
-          topology_(topology),
-          node_ids_(std::move(node_ids)),
-          property_id_(property_id)
-    {
-    }
+            core::PropertyId property_id);
 
-    core::ElementId id() const
-    {
-        return id_;
-    }
-
-    ElementTopology topology() const
-    {
-        return topology_;
-    }
-
-    const std::vector<core::NodeId>& node_ids() const
-    {
-        return node_ids_;
-    }
-
-    core::PropertyId property_id() const
-    {
-        return property_id_;
-    }
+    core::ElementId id() const;
+    ElementTopology topology() const;
+    const std::vector<core::NodeId>& node_ids() const;
+    core::PropertyId property_id() const;
 
 private:
     core::ElementId id_;

src/fesa/model/load.cpp

@@ -0,0 +1,25 @@
+#include <fesa/model/load.hpp>
+
+namespace fesa::model {
+
+Load::Load(core::NodeId node_id, DofComponent component, double value)
+    : node_id_(node_id), component_(component), value_(value)
+{
+}
+
+core::NodeId Load::node_id() const
+{
+    return node_id_;
+}
+
+DofComponent Load::component() const
+{
+    return component_;
+}
+
+double Load::value() const
+{
+    return value_;
+}
+
+} // namespace fesa::model

src/fesa/model/load.hpp

@@ -6,25 +6,11 @@ namespace fesa::model {
 
 class Load {
 public:
-    Load(core::NodeId node_id, DofComponent component, double value)
-        : node_id_(node_id), component_(component), value_(value)
-    {
-    }
+    Load(core::NodeId node_id, DofComponent component, double value);
 
-    core::NodeId node_id() const
-    {
-        return node_id_;
-    }
-
-    DofComponent component() const
-    {
-        return component_;
-    }
-
-    double value() const
-    {
-        return value_;
-    }
+    core::NodeId node_id() const;
+    DofComponent component() const;
+    double value() const;
 
 private:
     core::NodeId node_id_;

src/fesa/model/material.cpp

@@ -0,0 +1,22 @@
+#include <fesa/model/material.hpp>
+
+#include <utility>
+
+namespace fesa::model {
+
+Material::Material(core::MaterialId id, std::string name)
+    : id_(id), name_(std::move(name))
+{
+}
+
+core::MaterialId Material::id() const
+{
+    return id_;
+}
+
+const std::string& Material::name() const
+{
+    return name_;
+}
+
+} // namespace fesa::model

src/fesa/model/material.hpp

@@ -3,26 +3,15 @@
 #include <fesa/core/ids.hpp>
 
 #include <string>
-#include <utility>
 
 namespace fesa::model {
 
 class Material {
 public:
-    Material(core::MaterialId id, std::string name)
-        : id_(id), name_(std::move(name))
-    {
-    }
+    Material(core::MaterialId id, std::string name);
 
-    core::MaterialId id() const
-    {
-        return id_;
-    }
-
-    const std::string& name() const
-    {
-        return name_;
-    }
+    core::MaterialId id() const;
+    const std::string& name() const;
 
 private:
     core::MaterialId id_;

src/fesa/model/node.cpp

@@ -0,0 +1,20 @@
+#include <fesa/model/node.hpp>
+
+namespace fesa::model {
+
+Node::Node(core::NodeId id, std::array<double, 3> coordinates)
+    : id_(id), coordinates_(coordinates)
+{
+}
+
+core::NodeId Node::id() const
+{
+    return id_;
+}
+
+const std::array<double, 3>& Node::coordinates() const
+{
+    return coordinates_;
+}
+
+} // namespace fesa::model

src/fesa/model/node.hpp

@@ -8,20 +8,10 @@ namespace fesa::model {
 
 class Node {
 public:
-    Node(core::NodeId id, std::array<double, 3> coordinates)
-        : id_(id), coordinates_(coordinates)
-    {
-    }
+    Node(core::NodeId id, std::array<double, 3> coordinates);
 
-    core::NodeId id() const
-    {
-        return id_;
-    }
-
-    const std::array<double, 3>& coordinates() const
-    {
-        return coordinates_;
-    }
+    core::NodeId id() const;
+    const std::array<double, 3>& coordinates() const;
 
 private:
     core::NodeId id_;

src/fesa/model/property.cpp

@@ -0,0 +1,27 @@
+#include <fesa/model/property.hpp>
+
+#include <utility>
+
+namespace fesa::model {
+
+Property::Property(core::PropertyId id, std::string name, core::MaterialId material_id)
+    : id_(id), name_(std::move(name)), material_id_(material_id)
+{
+}
+
+core::PropertyId Property::id() const
+{
+    return id_;
+}
+
+const std::string& Property::name() const
+{
+    return name_;
+}
+
+core::MaterialId Property::material_id() const
+{
+    return material_id_;
+}
+
+} // namespace fesa::model

src/fesa/model/property.hpp

@@ -3,31 +3,16 @@
 #include <fesa/core/ids.hpp>
 
 #include <string>
-#include <utility>
 
 namespace fesa::model {
 
 class Property {
 public:
-    Property(core::PropertyId id, std::string name, core::MaterialId material_id)
-        : id_(id), name_(std::move(name)), material_id_(material_id)
-    {
-    }
+    Property(core::PropertyId id, std::string name, core::MaterialId material_id);
 
-    core::PropertyId id() const
-    {
-        return id_;
-    }
-
-    const std::string& name() const
-    {
-        return name_;
-    }
-
-    core::MaterialId material_id() const
-    {
-        return material_id_;
-    }
+    core::PropertyId id() const;
+    const std::string& name() const;
+    core::MaterialId material_id() const;
 
 private:
     core::PropertyId id_;

src/fesa/results/results.cpp

@@ -0,0 +1,70 @@
+#include <fesa/results/results.hpp>
+
+#include <stdexcept>
+#include <utility>
+
+namespace fesa::results {
+
+ResultFrame::ResultFrame(int frame_id, double time)
+    : frame_id_(frame_id), time_(time)
+{
+}
+
+int ResultFrame::frame_id() const
+{
+    return frame_id_;
+}
+
+double ResultFrame::time() const
+{
+    return time_;
+}
+
+void ResultFrame::add_field_output(FieldOutput output)
+{
+    if (output.components.empty()) {
+        throw std::invalid_argument("field output must have components");
+    }
+    if (output.entity_ids.size() * output.components.size() != output.values.size()) {
+        throw std::invalid_argument("field output values do not match row shape");
+    }
+    field_outputs_.push_back(std::move(output));
+}
+
+void ResultFrame::add_history_output(HistoryOutput output)
+{
+    history_outputs_.push_back(std::move(output));
+}
+
+const std::vector<FieldOutput>& ResultFrame::field_outputs() const
+{
+    return field_outputs_;
+}
+
+const std::vector<HistoryOutput>& ResultFrame::history_outputs() const
+{
+    return history_outputs_;
+}
+
+ResultStep::ResultStep(std::string name)
+    : name_(std::move(name))
+{
+}
+
+const std::string& ResultStep::name() const
+{
+    return name_;
+}
+
+ResultFrame& ResultStep::add_frame(int frame_id, double time)
+{
+    frames_.push_back(ResultFrame{frame_id, time});
+    return frames_.back();
+}
+
+const std::vector<ResultFrame>& ResultStep::frames() const
+{
+    return frames_;
+}
+
+} // namespace fesa::results

src/fesa/results/results.hpp

@@ -1,8 +1,6 @@
 #pragma once
 
-#include <stdexcept>
 #include <string>
-#include <utility>
 #include <vector>
 
 namespace fesa::results {
@@ -29,46 +27,14 @@ struct HistoryOutput {
 
 class ResultFrame {
 public:
-    ResultFrame(int frame_id, double time)
-        : frame_id_(frame_id), time_(time)
-    {
-    }
+    ResultFrame(int frame_id, double time);
 
-    int frame_id() const
-    {
-        return frame_id_;
-    }
-
-    double time() const
-    {
-        return time_;
-    }
-
-    void add_field_output(FieldOutput output)
-    {
-        if (output.components.empty()) {
-            throw std::invalid_argument("field output must have components");
-        }
-        if (output.entity_ids.size() * output.components.size() != output.values.size()) {
-            throw std::invalid_argument("field output values do not match row shape");
-        }
-        field_outputs_.push_back(std::move(output));
-    }
-
-    void add_history_output(HistoryOutput output)
-    {
-        history_outputs_.push_back(std::move(output));
-    }
-
-    const std::vector<FieldOutput>& field_outputs() const
-    {
-        return field_outputs_;
-    }
-
-    const std::vector<HistoryOutput>& history_outputs() const
-    {
-        return history_outputs_;
-    }
+    int frame_id() const;
+    double time() const;
+    void add_field_output(FieldOutput output);
+    void add_history_output(HistoryOutput output);
+    const std::vector<FieldOutput>& field_outputs() const;
+    const std::vector<HistoryOutput>& history_outputs() const;
 
 private:
     int frame_id_;
@@ -79,26 +45,11 @@ private:
 
 class ResultStep {
 public:
-    explicit ResultStep(std::string name)
-        : name_(std::move(name))
-    {
-    }
+    explicit ResultStep(std::string name);
 
-    const std::string& name() const
-    {
-        return name_;
-    }
-
-    ResultFrame& add_frame(int frame_id, double time)
-    {
-        frames_.push_back(ResultFrame{frame_id, time});
-        return frames_.back();
-    }
-
-    const std::vector<ResultFrame>& frames() const
-    {
-        return frames_;
-    }
+    const std::string& name() const;
+    ResultFrame& add_frame(int frame_id, double time);
+    const std::vector<ResultFrame>& frames() const;
 
 private:
     std::string name_;