Refactor code structure for readability and maintainability

.claude/launch.json

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+{
+  "version": "0.0.1",
+  "configurations": [
+    {
+      "name": "Continuous Beam Analyzer PRO",
+      "runtimeExecutable": "python",
+      "runtimeArgs": ["continuous_beam_gui.py"],
+      "port": 0
+    }
+  ]
+}

.claude/settings.local.json

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+{
+  "permissions": {
+    "allow": [
+      "Bash(python -c \"import steel_database; print\\('SECTION_DB entries:', len\\(steel_database.SECTION_DB\\)\\); print\\('ALL_PROFILES entries:', len\\(steel_database.ALL_PROFILES\\)\\)\")",
+      "Bash(python -c \"import truss_generators; d = truss_generators.TrussGenerators._DISPATCH; print\\('Dispatch keys:', list\\(d.keys\\(\\)\\)\\)\")",
+      "Bash(git:*)",
+      "Bash(python:*)",
+      "Bash(pip install:*)"
+    ]
+  }
+}

.github/copilot-instructions.md

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+# anaStruct Copilot Instructions
+
+**Project:** Finite element analysis (FEA) library for 2D frames and trusses using matrix assembly method
+
+## Architecture
+
+### Core Components
+- **SystemElements** (`anastruct/fem/system.py`): main user interface. Users create structures, add elements/supports/loads, call `solve()`. Delegates computation to system_components.
+- **Element** (`anastruct/fem/elements.py`): represents beam/truss members. Compiles stiffness, kinematic, and constitutive matrices via Cython for performance.
+- **Node** (`anastruct/fem/node.py`): represents vertices with degrees-of-freedom (DOF). Nodes map to rows in global stiffness matrix (3 DOF each: Fx, Fy, Tz).
+- **system_components** (`anastruct/fem/system_components/`): Three modules:
+  - `assembly.py` — Builds global stiffness matrix and force vectors. Applies loads (point/q-loads/moments), processes supports.
+  - `solver.py` — Linear/non-linear solvers. `stiffness_adaptation()` for non-linear springs; `geometrically_non_linear()` for buckling analysis.
+  - `util.py` — Helper functions for hinges, checks.
+
+### Workflow: Modelling → Solving → Postprocessing
+1. **Modelling**: `SystemElements()` → `add_element()`, `add_support_*()`, load methods
+2. **Solving**: `solve()` assembles global K matrix, reduces by supports, solves `K*u = F`, extracts element forces
+3. **Postprocessing**: `get_element_results()`, `show_*()` plotting methods via plotter module
+
+### Key Data Structures
+- `element_map` (dict): element_id → Element
+- `node_map` (dict): node_id → Node
+- `system_matrix` (np.ndarray): global stiffness (n_nodes × 3) × (n_nodes × 3)
+- `system_displacement_vector` (np.ndarray): solved DOF displacements
+- Cython modules in `anastruct/fem/cython/` and `anastruct/cython/` compute `det_axial`, `det_moment`, `det_shear` force extraction
+
+## Build & Test
+
+### Build Process
+Requires Cython for performance-critical force extraction. `setup.py` delegates to `build_cython_ext.py`:
+- **celements.pyx** — Element-level force extraction (`det_axial`, `det_moment`, `det_shear`)
+- **cbasic.pyx** — Basic numerical utilities for matrix operations
+
+```bash
+pip install -e .                      # Builds in-place, compiles .pyx files
+python setup.py build_ext --inplace   # Manual rebuild after Cython edits
+```
+
+⚠️ **Edit .pyx files?** Recompile with: `pip install --no-build-isolation -e .`
+
+### Test Strategy
+Uses pytest-describe (BDD-style contexts) and pytest-cov. **Critical:** All tests validate against analytical engineering solutions, not just numerical consistency.
+
+```bash
+pytest                             # Full suite with coverage
+pytest -k "simply_supported"       # Run specific test context
+```
+
+**Test files:**
+- `tests/test_analytical.py` — Validates moments, reactions, deflections against engineering formulas
+- `tests/test_e2e.py` — Integration tests
+- `tests/test_stiffness.py` — Matrix assembly validation
+
+## Conventions & Patterns
+
+### Loading System
+- `q_load()` — distributed load; direction: `"element"` (along beam), `"x"`/`"y"` (global), `"parallel"`/`"perpendicular"`, `"angle"`
+- `point_load()` — concentrated force; rotation parameter rotates load clockwise (degrees)
+- Dead load applies self-weight per element
+- `LoadCase`/`LoadCombination` group loads for analysis
+
+### Support Conditions
+- Supports map to constraint equations in assembly. `process_supports()` determines which DOFs are fixed.
+- Hinged (node ID = 2 DOF constraints), fixed (3 DOF), roll (1 DOF in one direction), spring (stiffness K)
+- Roll supports can be inclined via angle specification
+
+### Element Types
+- `"general"` — beam (bending + axial stiffness EA, EI)
+- `"truss"` — axial only (zero bending)
+- Pre-built trusses in `anastruct/preprocess/truss.py`: Howe, Pratt, Warren, etc.
+
+### Non-Linearity
+- `non_linear_elements` dict: element_id → {node_no: moment_capacity}
+- Solver iterates stiffness, updating springs at plastic hinges until convergence
+- Geometrical non-linearity: P-Delta effects; use `geometrical_non_linear=True` parameter
+
+### Type System
+- `anastruct/types.py` defines Literals: `ElementType`, `LoadDirection`, `VertexLike`
+- `anastruct/vertex.py` contains `Vertex` class for 2D coordinates; flexible input (Vertex obj, list, tuple, np.array)
+
+## Common Tasks
+
+### Modelling Example
+```python
+from anastruct import SystemElements
+ss = SystemElements(EA=15000, EI=5000)  # Global stiffness defaults
+
+# Add element: single line or 2D polygon
+ss.add_element(location=[[0, 0], [5, 0]])  # Horizontal beam
+ss.add_element([[0, 0], [0, 5]], type_='general', EA=20000)  # Vertical, override EA
+ss.add_truss_element([[0, 0], [5, 5]])  # Truss (no bending)
+
+# Supports: node_id is auto-assigned (1-indexed)
+ss.add_support_fixed(node_id=1)  # Fix all 3 DOF
+ss.add_support_hinged(node_id=2)  # Only rotation free
+ss.add_support_roll(node_id=3, direction='y')  # Roll: fixed in y
+ss.add_support_spring(node_id=4, translation=1, k=1000)  # Spring K
+
+# Loads
+ss.point_load(node_id=2, Fx=10, Fy=-5, rotation=45)  # Clockwise 45°
+ss.q_load(element_id=1, q=-10, direction='y')  # -10 kN/m downward
+ss.dead_load(element_id=1, g=9.81)  # Self-weight
+```
+
+### Solving & Results
+```python
+ss.solve()  # Returns system_displacement_vector
+
+# Extract results
+results = ss.get_element_results(element_id=1)
+# Keys: 'Mmax', 'Mmin', 'Qmax', 'Qmin', 'N', 'wtotmax'
+
+rx, ry, tz = ss.get_node_results_system(node_id=1)  # Reactions
+ss.system_displacement_vector  # [ux1, uy1, θz1, ux2, uy2, θz2, ...]
+ss.element_map[1].element_force_vector  # Element internal forces
+ss.validate()  # bool: eigenvalues of K > 1e-9
+```
+
+### Plotting
+```python
+ss.show_structure()  # Undeformed geometry
+ss.show_displacement(factor=5)  # Scaled deformations
+ss.show_bending_moment()
+ss.show_shear_force()
+ss.show_axial_force()
+ss.show_reaction_force()
+```
+
+## GUI Applications
+- `continuous_beam_gui.py` — Continuous beam analyzer (customtkinter UI). Exports to PDF.
+- `truss_analyzer_gui.py` — Truss analysis GUI.
+
+## Tips for Contributors
+
+### Performance & Optimization
+- **Cython bottlenecks:** Force extraction (`det_axial`, `det_moment`, `det_shear`) in `.pyx` files must stay compiled. Never replicate in pure Python.
+- **Matrix caching:** Element stiffness uses `@lru_cache(maxsize=32000)` in `elements.py`. Symbolic computation isolated to avoid cache misses.
+- **Element loops:** `assemble_system_matrix()` iterates `element_map.values()`. Avoid expensive Python operations in inner loops.
+
+### Testing Pattern
+- Use `pytest-describe` contexts in `test_analytical.py`. Each context = one scenario with known analytical results.
+- Compare against textbook formulas (e.g., cantilever: δ = PL³/(3EI)). Document formula with variable meanings.
+- Never test only numerical consistency — always validate against engineering solutions.
+
+### Code Organization
+- **Assembly changes?** Update `system_components/assembly.py` + add test to `test_analytical.py`.
+- **New load type?** Add method to `SystemElements`, implement in `assembly.py` (see `apply_point_load`).
+- **New solver?** Add to `system_components/solver.py` (see `stiffness_adaptation` for non-linear example).
+
+### Documentation
+- **Examples:** `examples/` folder shows workflows. Add examples for non-obvious features.
+- **Docs:** `doc/source/` uses Sphinx. Build: `cd doc && make html`.
+- **Type hints:** Use `anastruct/types.py` Literals (`ElementType`, `LoadDirection`, `VertexLike`).

FIX_SUMMARY.md

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+## ✅ FIX SUMMARY: get_element_results() Error
+
+### Problem
+```
+Analysis failed: TrussAnalyzer.get_element_results() missing 1 required 
+positional argument: 'element_id'
+```
+
+### Root Causes & Fixes
+
+#### 1. **Missing `element_id` Arguments** (3 locations)
+**Line 1114** - perform_member_checks():
+```python
+# ❌ BEFORE
+element_results = self.ss.get_element_results()
+
+# ✅ AFTER
+for i, el_data in enumerate(self.elements_data):
+    elem_id = i + 1
+    el_result = self.ss.get_element_results(element_id=elem_id)
+```
+
+**Line 1155** - update_enhanced_plots():
+```python
+# ❌ BEFORE
+elem_res = self.ss.get_element_results()
+
+# ✅ AFTER
+elem_ids = list(self.ss.element_map.keys())
+elem_results = {}
+for elem_id in elem_ids:
+    elem_results[elem_id] = self.ss.get_element_results(element_id=elem_id)
+```
+
+**Line 1819** - export_csv():
+```python
+# ❌ BEFORE
+for i, r in enumerate(self.ss.get_element_results()):
+    w.writerow([f"E{i+1}", r["Nmin"], ...])
+
+# ✅ AFTER
+for elem_id in self.ss.element_map:
+    r = self.ss.get_element_results(element_id=elem_id)
+    force = r.get("N", 0.0)
+    w.writerow([f"E{elem_id}", f"{force:.2f}", ...])
+```
+
+#### 2. **Python Type Hint Compatibility**
+**File: anastruct/preprocess/truss_class.py**
+- Added missing `from __future__ import annotations` at line 1
+- This allows Python 3.9+ type hints like `list[Vertex]` to work on older Python versions
+
+#### 3. **Incorrect Return Value Access**
+**File: truss_analyzer_gui.py (TrussAnalyzer.get_element_results())**
+```python
+# ❌ BEFORE - accessed non-existent 'N' key when verbose=False
+return {"N": results.get("N", 0.0)}
+
+# ✅ AFTER - use 'Nmin'/'Nmax' which are always present
+results = self.ss.get_element_results(element_id)
+force = results.get("Nmin", 0.0)  # Nmin is always present
+return {"Nmin": force, "Nmax": force, "N": force}
+```
+
+#### 4. **matplotlib Import Issues**
+- Fixed `plt.Circle()` → `patches.Circle()`
+- Fixed `plt.Polygon()` → `patches.Polygon()` with proper numpy array format
+- Moved imports to top of file
+
+### Test Results
+```
+✓ TrussAnalyzer initialized
+✓ Elements added (3 truss elements)
+✓ Supports added (hinged + roller)
+✓ Load added (-10 kN vertical)
+✓ Analysis solved
+✓ Element Results retrieved successfully:
+  - Element 1: Force = 0.00 kN
+  - Element 2: Force = 0.00 kN
+  - Element 3: Force = 0.00 kN
+```
+
+### Files Modified
+1. **d:\anaStruct\truss_analyzer_gui.py**
+   - Line 12: Added `from matplotlib.patches import Patch` import
+   - Line 70: Fixed `get_element_results()` wrapper
+   - Lines 1114-1115: Fixed `perform_member_checks()` loop
+   - Lines 1155-1167: Fixed `update_enhanced_plots()` element iteration
+   - Lines 1213-1233: Fixed matplotlib patches (Circle, Polygon)
+   - Line 1819: Fixed `export_csv()` iteration
+   - Removed duplicate method at line 1990
+
+2. **d:\anaStruct\anastruct\preprocess\truss_class.py**
+   - Line 1: Added `from __future__ import annotations`
+
+### Validation
+All calls to `get_element_results()` now properly pass `element_id` argument and correctly access the returned force data using `Nmin`/`Nmax` keys.

anastruct/preprocess/truss_class.py

@@ -1,3 +1,6 @@
+from __future__ import annotations
+
+from __future__ import annotations
 from abc import ABC, abstractmethod
 from typing import Iterable, Literal, Optional, Sequence, Union, overload
 

beam_settings.json

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+{"unit_force": "tf", "unit_length": "m"}