core.nula

// Nulang standard library — core combinators and utilities.
// Language version: 2.0.0-alpha
// Import: `import stdlib::core`

// ── Identity and constants ────────────────────────────────────────────────

/// Identity function. Returns its argument unchanged.
pub fn identity(x) { x }

/// Constant function: always returns the first argument, ignoring the second.
pub fn const_fn(x, _y) { x }

/// Always: given a value, returns a function that ignores its input and returns that value.
pub fn always(x) { fn(_y) { x } }

// ── Function combinators ──────────────────────────────────────────────────

/// Apply function f to argument x.
pub fn apply(f, x) { f(x) }

/// Function composition (3-arg form): (f ∘ g)(x) = f(g(x)).
pub fn compose(f, g, x) { f(g(x)) }

/// Returns a new function h(x) = f(g(x)).
pub fn compose_fn(f, g) { fn(x) { f(g(x)) } }

/// Flip argument order: flip(f, x, y) = f(y, x).
pub fn flip(f, x, y) { f(y, x) }

// ── Boolean combinators ───────────────────────────────────────────────────

/// Logical negation.
pub fn negate(b) { if b then false else true }

// ── Comparison helpers ────────────────────────────────────────────────────

/// Clamp x to the range [lo, hi].
pub fn clamp(x, lo, hi) {
    if x < lo then lo
    else if x > hi then hi
    else x
}

/// True when x is between lo and hi (inclusive).
pub fn between(lo, hi, x) { lo <= x && x <= hi }