fizzbuzz.js

gistfile1.js

// FizzBuzz up to 20 using only S and K combinators

// Basic combinators
let S = (x) => (y) => (z) => x(z)(y(z));
let K = (x) => (y) => x;

// Identity (I = S K K)
let I = S(K)(K);

// Boolean logic
let TRUE = K;  // λx.λy.x - returns first argument
let FALSE = (x) => (y) => y;  // λx.λy.y - returns second argument
let IF = (cond) => (then) => (else_) => cond(then)(else_);

// Church numerals using successor
let ZERO = FALSE;
let SUCC = (n) => (f) => (x) => f(n(f)(x));  // Successor
let ONE = I;
let TWO = SUCC(ONE);
let THREE = SUCC(TWO);
let FOUR = SUCC(THREE);
let FIVE = SUCC(FOUR);
let SIX = SUCC(FIVE);
let SEVEN = SUCC(SIX);
let EIGHT = SUCC(SEVEN);
let NINE = SUCC(EIGHT);
let TEN = SUCC(NINE);
let ELEVEN = SUCC(TEN);
let TWELVE = SUCC(ELEVEN);
let THIRTEEN = SUCC(TWELVE);
let FOURTEEN = SUCC(THIRTEEN);
let FIFTEEN = SUCC(FOURTEEN);
let SIXTEEN = SUCC(FIFTEEN);
let SEVENTEEN = SUCC(SIXTEEN);
let EIGHTEEN = SUCC(SEVENTEEN);
let NINETEEN = SUCC(EIGHTEEN);
let TWENTY = SUCC(NINETEEN);

// Arithmetic operations
let ADD = (m) => (n) => m(SUCC)(n);
let MULT = (m) => (n) => m(ADD(n))(ZERO);
let PRED = (n) => (f) => (x) => n((g) => (h) => h(g(f)))((u) => x)((u) => u);  // Predecessor
let SUB = (m) => (n) => n(PRED)(m);

// Comparison
let ISZERO = (n) => n((x) => FALSE)(TRUE);
let LEQ = (m) => (n) => ISZERO(SUB(m)(n));

// Modulo operation (simplified for small numbers)
let MOD_ONCE = (m) => (n) => IF(LEQ(n)(m))(SUB(m)(n))(m);
let MOD = (m) => (n) => MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(
  MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(MOD_ONCE(
  m)(n))(n))(n))(n))(n))(n))(n))(n))(n))(n))(n))(n))(n))(n))(n))(n))(n))(n))(n))(n);

// Divisibility checks
let DIVISIBLE_BY_3 = (n) => ISZERO(MOD(n)(THREE));
let DIVISIBLE_BY_5 = (n) => ISZERO(MOD(n)(FIVE));

// Convert Church numeral to JavaScript number
let CHURCH_TO_JS = (n) => n((x) => x + 1)(0);

// String representations (simplified - using functions that return strings)
let FIZZ_STR = () => "Fizz";
let BUZZ_STR = () => "Buzz";
let FIZZBUZZ_STR = () => "FizzBuzz";
let NUM_TO_STR = (n) => () => CHURCH_TO_JS(n).toString();

// FizzBuzz logic
let FIZZBUZZ_LOGIC = (n) => IF(DIVISIBLE_BY_3(n))(
  IF(DIVISIBLE_BY_5(n))(FIZZBUZZ_STR)(FIZZ_STR)
)(
  IF(DIVISIBLE_BY_5(n))(BUZZ_STR)(NUM_TO_STR(n))
);

// Recursive function to print from 1 to 20
let PRINT_RANGE = (start) => (end) => IF(LEQ(start)(end))(
  () => {
    console.log(FIZZBUZZ_LOGIC(start)());
    PRINT_RANGE(SUCC(start))(end)();
  }
)(
  () => {}  // Do nothing
);

// Execute FizzBuzz from 1 to 20
PRINT_RANGE(ONE)(TWENTY)();