var_context builder

Description

MatrixXd m(3, 2); 
...
var_context vc
  = var_context::builder()
    .matrix("a", m)
    .real("f", 2.3)
    .build();

Contributor guide

Tech stack

cpp

Domain

developer experiencetesting

Issue type

feature

DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.

3

Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.

half day

Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.

fresh

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

clear

Prerequisites

C++ builder patternStan var context class

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

60

Research direction

The issue requests a builder pattern for `var context` to simplify test construction. The implementation should be done in the existing C++ source code, likely in `src/stan/io/var context.hpp` or similar. A builder class with methods like `matrix()` and `real()` should be added, culminating in a `build()` method that returns a `var context`. No existing PRs or comments provide additional guidance; the developer should design the builder according to typical C++ builder patterns and ensure compatibility with the existing `var context` interface.