omdEquationSequenceNode

Represents a sequence of mathematical steps, typically a series of equations that show the process of solving a problem. This node is a container that manages the layout, alignment, and simplification history of its steps.

Class: omdEquationSequenceNode extends omdNode

import { omdEquationSequenceNode } from './omd/nodes/omdEquationSequenceNode.js';

Constructor

new omdEquationSequenceNode(steps)

Parameters:

• steps {Array<omdNode>} - An array of nodes (usually omdEquationNode or omdOperationDisplayNode) that make up the sequence.

Static Methods

fromSteps(stepsArray)

Creates an omdEquationSequenceNode from an array of expression strings.

const sequence = omdEquationSequenceNode.fromSteps([
    '2x + 4 = 10',
    '2x = 6',
    'x = 3'
]);

• Parameters:
  • stepsArray {Array} - An array of strings, where each string is a step (either an equation or an expression).
• Returns: omdEquationSequenceNode A new instance.
• Throws: Error if a string is not a valid equation or expression, or if math.js is not available.

Core Methods

addStep(step, options)

Adds a new step to the end of the sequence.

• Parameters:
  • step {omdNode | string} - The node or expression string to add. If a string, it is parsed as an equation or expression.
  • options {Object|string} (optional) - Options for the step, such as description and stepMark (importance level), or a description string for backward compatibility.
  • importance {number} (optional) - Importance level (0, 1, or 2) if using legacy signature.
• Returns: number - The index of the newly added step.

simplify()

Applies one round of simplification to the last step in the sequence and adds the result as a new step.

• Returns: Object - An object detailing the result: { success, foldedCount, isFinalSimplification, message }.

simplifyAll(maxIterations)

Repeatedly calls simplify() on the last step until no more simplifications can be applied or the iteration limit is reached.

• Parameters:
  • maxIterations {number} (optional) - A safeguard against infinite loops. Defaults to 50.
• Returns: Object - An object summarizing the process: { success, totalSteps, iterations, message }.

applyEquationOperation(value, operation)

Applies an operation (e.g., 'add', 'subtract', 'multiply', 'divide') to both sides of the last equation in the sequence. This typically adds two new steps: a visual display of the operation and the resulting new equation.

• Parameters:
  • value {number} - The value to apply.
  • operation {string} - The name of the operation ('add', 'subtract', 'multiply', 'divide').
• Returns: omdEquationSequenceNode The sequence instance, for chaining.

applyEquationFunction(functionName)

Applies a function (e.g., 'sqrt') to both sides of the last equation and adds the result as a new step.

• Parameters:
  • functionName {string} - The name of the function.
• Returns: omdEquationSequenceNode The sequence instance, for chaining.

Other Key Methods

• getCurrentEquation(): Returns the last omdEquationNode in the sequence, or null if none.
• getCurrentStep(): Returns the current step node (may not be an equation).
• getSimplificationHistory(): Returns an array of all simplification events that have occurred.
• rebuildNodeMap(): Re-indexes all nodes within the sequence, which is crucial for provenance tracking and highlighting.
• updateStepsVisibility(predicate): Shows or hides steps based on a provided function, useful for filtering and UI.
• clear(): Removes all steps and history from the sequence.
• navigateToStep(index): Navigates to a specific step by index.
• nextStep(), previousStep(): Navigate forward/backward through steps.

Layout and Provenance

The omdEquationSequenceNode automatically aligns all omdEquationNode steps by their equals signs, creating a clean, readable layout. It also tracks provenance for all nodes, supporting step-by-step highlighting and history.

Example

// Create a sequence with an initial equation
const sequence = omdEquationSequenceNode.fromSteps([
  '2 * (x + 1) = 10'
]);

// Apply operations and simplifications
sequence.applyEquationOperation(2, 'divide'); // Adds a step: (2*(x+1))/2 = 10/2
sequence.simplifyAll(); // Simplifies to x+1=5, then x=4

// Add the sequence to a display
const display = new omdDisplay(document.getElementById('container'));
display.render(sequence);

See Also

• omdNode - The base class.
• omdEquationNode - The primary type of node held within a sequence.
• omdStepVisualizer - A subclass that adds interactive dots and explanations to the sequence.