charts.palette

pub fn palette(scheme: &str, count: i64, cycle: bool) -> Vec<String>

fune!(charts.palette@^1);  // then call palette(…)

use super::funejson::Value;  ← the fune runtime: the JSON value the test vectors use; fune build keeps it only where a signature takes one
use super::charts_palette_data::PALETTES;  ← this capability’s own data, compiled from data/palettes.json into the same file by fune build

/// The first `count` colours of a named categorical scheme, in its order.
/// Asking for more colours than the scheme has is an error unless `cycle`
/// says repeating them is acceptable.
///
/// # Panics
/// Panics on an unknown scheme, a negative count, or too many colours
/// without `cycle`.
pub fn palette(scheme: &str, count: i64, cycle: bool) -> Vec<String> {
    let mut rows: Vec<_> = PALETTES.iter().filter(|c| c.scheme == scheme).collect();
    rows.sort_by_key(|c| c.position);
    let colours: Vec<String> = rows.iter().map(|c| c.hex.to_string()).collect();
    if colours.is_empty() {
        panic!("unknown palette \"{}\"; use okabe-ito or tol-bright", scheme);
    }
    if count < 0 {
        panic!("count must be a whole number of at least 0, received {}", count);
    }
    if count as usize > colours.len() && !cycle {
        panic!("palette \"{}\" has only {} colours; pass cycle to repeat them", scheme, colours.len());
    }
    (0..count as usize).map(|i| colours[i % colours.len()].clone()).collect()
}

pub fn fune_vector(args: &[Value]) -> Value {
    let out = palette(args[0].as_str(), args[1].as_i64(), args[2].as_bool());
    Value::Arr(out.iter().map(|s| Value::str(s)).collect())
}

Install

fune build

With that line in your source, in a Rust project (language rust in fune.project), fune build resolves it and nothing else, pins them in fune.lock, downloads only the Rust package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. A crate’s build.rs runs it before every compile. Or pin a range in fune.project and build in one step:

fune add charts.palette

The manifest, vectors and README with only the Rust implementation. Install it without the registry with fune add ./charts.palette-1.0.0-rust.fune, or fetch it from a terminal with fune pull charts.palette@1.0.0:rust.

The whole function, every language, is one file too: charts.palette-1.0.0.fune, 10,984 bytes, sha256 ddf253584a9c2cad154b151e0ff42da0782096c9ab4744064ea04fc36c25b126. It installs into a project of any language.

// fune: before charts.palette

// fune: after charts.palette

// fune: step charts.palette after <n|label>

More from the author

The colours are data (`data/palettes.json`, one row per colour with its position and name), not code. They describe fixed published schemes rather than rules that change over time, so the file has no `effective` columns and is never pruned.

Asking for more colours than a scheme has is an error unless `cycle` is true: a ninth series quietly reusing the first colour makes two series look like one. With `cycle`, colours repeat from the start. All hex is lowercase `#rrggbb`.

Sources: M. Okabe and K. Ito, "Color Universal Design (CUD): How to make figures and presentations that are friendly to colorblind people" (2002, rev. 2008), https://jfly.uni-koeln.de/html/color_blind/ (RGB 0-255 values: black 0,0,0; orange 230,159,0; sky blue 86,180,233; bluish green 0,158,115; yellow 240,228,66; blue 0,114,178; vermillion 213,94,0; reddish purple 204,121,167); B. Wong, "Points of view: Color blindness", Nature Methods 8, 441 (2011); P. Tol, "Colour Schemes" (SRON technical note SRON/EPS/TN/09-002, 2021), https://sronpersonalpages.nl/~pault/ (bright: #4477AA, #EE6677, #228833, #CCBB44, #66CCEE, #AA3377, #BBBBBB).

Files