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Planar truss span grammar problem
=================================

A discrete topology grammar for adding and removing joints and members in a planar truss.

See :doc:`../grammar` for the grammar family index.

Quick Facts
-----------

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   * - Field
     - Value
   * - Problem ID
     - ``planar_truss_span``
   * - Problem Family
     - grammar
   * - Implementation
     - ``design_research_problems.problems.grammar._planar_truss:PlanarTrussSpanProblem``
   * - Capabilities
     - ``discrete-actions``, ``external-adapter``, ``optional-evaluator``, ``serializable-state``, ``statement-markdown``
   * - Study Suitability
     - none
   * - Tags
     - ``grammar``, ``truss``, ``discrete``, ``topology``

Taxonomy
--------

Formulation
   discrete_grammar
Convexity
   not_applicable
Design Variable Type
   discrete
Is Dynamic
   no
Orientation
   engineering_practical
Feasibility Ratio Hint
   0.25
Objective Mode
   single
Constraint Nature
   hard
Bounds Summary
   planar topology over a fixed span and height envelope
Tags
   ``grammar``, ``truss``, ``discrete``, ``topology``

Statement
---------

Create a stable, lightweight planar truss spanning a fixed distance between a left pinned support and a right roller support. The grammar begins with the supports and one loaded free joint. Designers can add interior joints, add members, and remove members.

States are evaluated by translating the library-owned grammar state into a fresh ``trussme.Truss``, applying the load, and attempting a structural analysis. Singular or unstable states are treated as infeasible results.

Problem Shape
-------------

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   * - Field
     - Value
   * - State Type
     - PlanarTrussState
   * - Initial Transition Count
     - 6
   * - Initial Rule Names
     - ``add_joint``, ``add_member``

Manifest Parameters
-------------------

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   * - Key
     - Value
   * - load_magnitude
     - 1000
   * - max_height
     - 5
   * - span
     - 10

Initial Transition Summary
--------------------------

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   * - Rule Name
     - Transition Count
   * - add_joint
     - 3
   * - add_member
     - 3

Library Interface
-----------------

- ``initial_state()``
- ``enumerate_transitions(state)``
- ``enumerate_next_states(state)``
- ``evaluate(state)``