=>

const x = list(1,list(2, list(3,4),5), list(6,7)); function tree_map(func, tree){ return map(sub_tree=> is_pair(sub_tree) ? tree_map(func, sub_tree) : func(sub_tree), tree); } function suquare_tree(tree){ return tree_map(square,tree); } suquare_tree(x)//[1, [[4, [[9, [16, null]], [25, null]]], [[36, [49, null]], null]]];

function square_tree(tree){ return is_null(tree) ? null : ! is_pair(tree) ? square(tree) : pair(square_tree(head(tree)), square_tree(tail(tree))); } function square_tree_map(tree){ return map(sub_tree => is_pair(sub_tree) ? square_tree_map(sub_tree) : square(sub_tree),tree); }

function for_each(fun, list){ fun(head(list)); return is_null(tail(list)) ? true : for_each(fun, tail(list)); } function for_each_map(fun, list){ map(fun, list); } 반환값이 정해지지 않았기 때문에(적용할 함수가 돌려주는 인자를 변환하는 게 아닌 side effect임) 여러 방식의 구현이 가능하다.

function square(x){ return x * x; } function map(fun, items) { return is_null(items) ? null : pair(fun(head(items)), map(fun, tail(items))); } function square_list(items){ return is_null(items) ? null : pair(square(head(items)), square_list(tail(items))); } function square_list_m(items){ return map(square, items); }

function plus_curried(x){ return y => x + y; } function brooks(f, list){ return is_null(list) ? f : brooks(f(head(list)), tail(list)); } function brooks_curried(list){ return brooks(head(list), tail(list)); } brooks_curried(list(brooks_curried, list(plus_curried, 3, 4))); brooks_curried(list(brooks_curried, list(brooks_curried, list(plus_curried, 3, 4)))); 두 문장 모두 7로 평가된다.

function last_pair(items){ return is_null(tail(items)) ? items : last_pair(tail(items)); } 꼬리를 돌려주면서 꼬리의 꼬리가 null이면 그대로 꼬리를 반환한다.

function make_point(x, y){ return pair(x, y); } function x_point(p){ return head(p); } function y_point(p){ return tail(p); } function make_segment(start, end) { return pair(start, end) } function start_segment(s){ return head(s); } function end_segment(s){ return tail(s); } function midpoint_segment(s){ return make_point( x_point(start_segment(s))+x_point(end_segment(s))/2, y_point(start_segmen..

function abs(x){ return x 0 ? pair(abs(n), abs(d)) : n < 0 ? pair(n, d) : pair(-n, abs(d)); }

function compose(f, g){ return x=> f(g(x)); }

function double(f){ return x => f(f(x)); } function inc(x){ return x+1; } double(double(double))(inc)(5)//21 double이 3번 적용되므로 함수는 16번 실행된다