Add a way to plot the output from generators

For visualization, add a simple script for generating scatter plots and
a binary (via examples) to plot the inputs given various domains.

.gitignore

@@ -7,3 +7,6 @@
 Cargo.lock
 musl/
 **.tar.gz
+
+# Files generated by binaries
+build/

crates/libm-test/examples/plot_domains.rs

@@ -0,0 +1,58 @@
+//! Program to write all inputs from a generator to a file, then invoke a Julia script
+//! to plot them. Requires Julia with the `CairoMakie` dependency.
+//!
+//! Note that running in release mode by default generates a _lot_ more datapoints, which
+//! causes plotting to be extremely slow (some simplification to be done in the script).
+
+use std::io::{BufWriter, Write};
+use std::path::Path;
+use std::process::Command;
+use std::{env, fs};
+
+use libm_test::domain::Domain;
+use libm_test::gen::domain_logspace;
+
+const JL_PLOT: &str = "examples/plot_file.jl";
+
+fn main() {
+    let out_dir = Path::new("build");
+    if !out_dir.exists() {
+        fs::create_dir(out_dir).unwrap();
+    }
+
+    let jl_script = Path::new(&env::var("CARGO_MANIFEST_DIR").unwrap()).join(JL_PLOT);
+    let mut j_args = Vec::new();
+
+    // Plot a few domains with some functions that use them.
+    plot_one(out_dir, "sqrt", Domain::SQRT, &mut j_args);
+    plot_one(out_dir, "cos", Domain::TRIG, &mut j_args);
+    plot_one(out_dir, "cbrt", Domain::UNBOUNDED, &mut j_args);
+
+    println!("launching script");
+    let mut cmd = Command::new("julia");
+    if !cfg!(debug_assertions) {
+        cmd.arg("-O3");
+    }
+    cmd.arg(jl_script).args(j_args).status().unwrap();
+}
+
+/// Plot a single domain.
+fn plot_one(out_dir: &Path, name: &str, domain: Domain<f32>, j_args: &mut Vec<String>) {
+    let base_name = out_dir.join(format!("domain-inputs-{name}"));
+    let text_file = base_name.with_extension("txt");
+
+    {
+        // Scope for file and writer
+        let f = fs::File::create(&text_file).unwrap();
+        let mut w = BufWriter::new(f);
+
+        for input in domain_logspace::get_test_cases_inner::<f32>(domain) {
+            writeln!(w, "{:e}", input.0).unwrap();
+        }
+        w.flush().unwrap();
+    }
+
+    // The julia script expects `name1 path1 name2 path2...` args
+    j_args.push(name.to_owned());
+    j_args.push(base_name.to_str().unwrap().to_owned());
+}

crates/libm-test/examples/plot_file.jl

@@ -0,0 +1,113 @@
+"A quick script to for plotting a list of floats.
+
+Takes a list of floats and a real function, plots both on a graph in both
+linear and log scale. Requires [Makie] (specifically CairoMakie) for plotting.
+
+[Makie]: https://docs.makie.org/stable/
+"
+
+using CairoMakie
+
+CairoMakie.activate!(px_per_unit=10)
+
+"Apply a function, returning the default if there is a domain error"
+function map_or_default(
+    input::AbstractFloat,
+    f::Function,
+    default::AbstractFloat
+)::AbstractFloat
+    try
+        return f(input)
+    catch
+        return default
+    end
+end
+
+"Read inputs from a file, create both linear and log plots"
+function plot_one(
+    fig::Figure,
+    base_name::String,
+    fn_name::String,
+    f::Function;
+    xlims::Union{Tuple{Any,Any},Nothing},
+    xlims_log::Union{Tuple{Any,Any},Nothing},
+)::Nothing
+    float_file = "$base_name.txt"
+    lin_out_file = "$base_name.png"
+    log_out_file = "$base_name-log.png"
+
+    if xlims === nothing
+        xlims = (-6, 6)
+    end
+    if xlims_log === nothing
+        xlims_log = (xlims[1] * 500, xlims[2] * 500)
+    end
+
+    inputs = readlines(float_file)
+
+    # Parse floats
+    x = map((v) -> parse(Float32, v), inputs)
+    # Apply function to the test points
+    y = map((v) -> map_or_default(v, f, 0.0), x)
+
+    # Plot the scatter plot of our checked values as well as the continuous function
+    ax = Axis(fig[1, 1], limits=(xlims, nothing), title=fn_name)
+    lines!(ax, xlims[1] .. xlims[2], f, color=(:blue, 0.4))
+    scatter!(ax, x, y, color=(:green, 0.3))
+    save(lin_out_file, fig)
+    delete!(ax)
+
+    # Same as above on a log scale
+    ax = Axis(
+        fig[1, 1],
+        limits=(xlims_log, nothing),
+        xscale=Makie.pseudolog10,
+        title="$fn_name (log scale)"
+    )
+    lines!(ax, xlims_log[1] .. xlims_log[2], f, color=(:blue, 0.4))
+    scatter!(ax, x, y, color=(:green, 0.3))
+    save(log_out_file, fig)
+    delete!(ax)
+end
+
+# Args alternate `name1 path1 name2 path2`
+fn_names = ARGS[1:2:end]
+base_names = ARGS[2:2:end]
+
+for idx in eachindex(fn_names)
+    fn_name = fn_names[idx]
+    base_name = base_names[idx]
+
+    xlims = nothing
+    xlims_log = nothing
+
+    fig = Figure()
+
+    # Map string function names to callable functions
+    if fn_name == "cos"
+        f = cos
+        xlims_log = (-pi * 10, pi * 10)
+    elseif fn_name == "cbrt"
+        f = cbrt
+        xlims = (-2.0, 2.0)
+    elseif fn_name == "sqrt"
+        f = sqrt
+        xlims = (-1.1, 6.0)
+        xlims_log = (-1.1, 5000.0)
+    else
+        println("unrecognized function name `$fn_name`; update plot_file.jl")
+    end
+
+    println("plotting $fn_name")
+    plot_one(
+        fig,
+        base_name,
+        fn_name,
+        f,
+        xlims=xlims,
+        xlims_log=xlims_log,
+    )
+end
+
+base_name = ARGS[1]
+fn_name = ARGS[2]