Replay Composition

Function Step Replay

Call and Return

A function call is a compact replay composition: the caller pauses, the callee produces a value, and the caller continues with the result.

Program

Play the program to choose a request count and watch the replay move through the helper before returning to main.

function_step_replay_rust.rs 
fn score_bonus(count: i32) -> i32 {
    let points = count * 2;
    points
}

fn main() {
    let request_count = ;
    let base_score = 10;
    let bonus = score_bonus(request_count);
    let total = base_score + bonus;
    println!("{request_count}:{total}");
}

fn score_bonus(count: i32) -> i32 {
    let points = count * 2;
    points
}

fn main() {
    let request_count = ;
    let base_score = 10;
    let bonus = score_bonus(request_count);
    let total = base_score + bonus;
    println!("{request_count}:{total}");
}

fn score_bonus(count: i32) -> i32 {
    let points = count * 2;
    points
}

fn main() {
    let request_count = ;
    let base_score = 10;
    let bonus = score_bonus(request_count);
    let total = base_score + bonus;
    println!("{request_count}:{total}");
}
callee state The helper owns `count` and `points` while it runs.
return value The last expression returns the computed points to the caller.
single stream The replay is still one source panel and one ordered event stream.