(define (identity x) x)

(syntax ($identity x) x)

(define (bind-1-of-2 function constant)
  (lambda (x) (function constant x)))

(syntax ($bind-1-of-2 function constant)
  (lambda ($x) (function constant $x)))

(define (bind-2-of-2 function constant)
  (lambda (x) (function x constant)))

(syntax ($bind-2-of-2 function constant)
  (lambda ($x) (function $x constant)))

(define (S-combinator f g)
  (lambda (x) (f x) (g x)))

(syntax ($S-combinator f g)
  (lambda ($x) (f $x) (g $x)))

(define (compose f g)
  (lambda (x) (f (g x))))

(syntax ($compose f g)
  (lambda ($x) (f (g $x))))

(define (D-combinator function)
  (lambda (x) (function x x)))

(syntax ($D-combinator function)
  (lambda ($x) (function $x $x)))

(define (T-combinator f)
  (lambda (x y) (f y x)))

(syntax ($T-combinator f)
  (lambda ($x $y) (f $y $x)))

(define (if-combinator predicate f g)
  (lambda (x) (if (predicate x) (f x) (g x))))

(syntax ($if-combinator predicate f g)
  (lambda ($x) (if (predicate $x) (f $x) (g $x))))

(define (when-combinator predicate function)
  (lambda (x) (if (predicate x) (function x))))

(syntax ($when-combinator predicate function)
  (lambda ($x) (if (predicate $x) (function $x))))