070 step basic

// TEST: kernel:step - kernel-native iteration wrapping kernel ops
// step(0..N) wraps the kernel ops that follow it in the continuation chain.
//
// Data: 3 bodies with mass = 1.0, 2.0, 3.0
// step(0..3) wrapping self { k.mass += 0.2 }
// Each iteration: each body gains +0.2
// After 3 iterations: 1.6, 2.6, 3.6

~import std/kernel
~import std/io

~std/kernel:shape(Body) {
    mass: f64,
}

~std/kernel:init(Body) {
    { mass: 1.0 },
    { mass: 2.0 },
    { mass: 3.0 },
}
| kernel k |> std/kernel:step(0..3)
    | step |> std/kernel:self { k.mass += 0.2 }
| computed c |> std/io:print.blk {
        mass[0]={{ c[0].mass:f }} mass[1]={{ c[1].mass:f }} mass[2]={{ c[2].mass:f }}
    }