Diff

As explained in Data-Oriented Programming: Reduce software complexity

A diff is a representation of the changes between two versions of structured data.

A diff represents the changes between two versions of structured data. For nested maps, it identifies changed fields and preserves their paths, turning a vague “something changed” into information that reconciliation can use. section 5.2 section 9.4.4

Suppose two mutations begin from previous state. Compare previous with current to see what another mutation changed, then compare previous with next to see what this mutation wants. Disjoint diffs can be combined; overlapping fields indicate a conflict and can cause the mutation to abort. section 5.2 section 5.5

A focused change

Comparing {y: {z: 1}, w: [5]} with {y: {z: 2}, w: [4]} produces a diff containing only y.z = 2 and w = [4].

Figure 5.4 In a three-way merge, we calculate the diff between previous and next, and we apply it to current.

Visualize how a diff from previous to next is applied to current during a three-way merge. section 5.2

How Data-Oriented Programming: Reduce software complexity covers it

How deep it goes

Explains recursive structural comparison and three-way conflict detection, while deferring thread-safe implementation for multithreaded environments.

Examples

Demonstrates changed nested fields and arrays with immutable maps, then tests the resulting sparse structural diff.

What it assumes

Assumes familiarity with nested maps, immutable data, and concurrent mutations while explaining the comparison procedure directly.

What you can do after

Diagnose concurrent state changes and implement recursive diffs for immutable nested data.

How it connects

Connects diffs to three-way merge, optimistic concurrency control, immutable data, persistent data structures, and Git.

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Also explained in

• 

  liveBookmanning.com
  Coding with AIA diff is a representation of additions, deletions, and other differences between two versions of text or data.

Compare how 2 books explain diff →

Related concepts

• dynamic programmingused by · Dynamic programming is an algorithmic technique that solves problems by decomposing them into overlapping subproblems and storing or reusing their solutions.
• three-way mergeused by · A three-way merge combines changes by comparing two divergent versions with their common predecessor.
• pytestproduced by · pytest is a Python testing framework for discovering, writing, and running automated tests.
• file objectuses · A file object is a program-accessible representation of an open file or stream, including its access state and input/output operations.

This explainer was generated by Manning's knowledge graph from the text of Data-Oriented Programming: Reduce software complexity. The section links point to the parts of the book it draws on.