require "table2"
local fmt = require "fmt"

local function rng(modifier)
    while true do
        local r1 = math.random()
        local r2 = math.random()
        if r2 < modifier(r1) then return r1 end
    end
end

local modifier = |x| -> (x < 0.5) ? 2 * (0.5 - x) : 2 * (x - 0.5)

$define N = 100000
$define NUM_BINS = 20
$define HIST_CHAR = "■"
$define HIST_CHAR_SIZE = 125

local bins = table.rep(NUM_BINS, 0)
local bin_size = 1 / NUM_BINS
for i = 1, N do
    local rn = rng(modifier)
    local bn = rn // bin_size
    bins[bn + 1] += 1
end

fmt.print($"Modified random distribution with %,s samples in range [0, 1):\n", N)
print("    Range           Number of samples within that range")
for i = 0, NUM_BINS - 1 do
    local hist = string.rep(HIST_CHAR, math.round(bins[i + 1] / HIST_CHAR_SIZE))
    fmt.print("%4.2f ..< %4.2f  %s %,s", bin_size * i, bin_size * (i + 1), hist, bins[i + 1])
end