Building Abstractions with Functions - Formulating Abstractions with Higher-Order Functions - Functions as Arguments - linear recursion, iteration
Structure and Interpretation of Computer Programs: JavaScript Edition(Harold Abelson(著)、Gerald Jay Sussman(著)、Julie Sussman(著)、The MIT Press)のChapter 1(Building Abstractions with Functions)、1.3(Formulating Abstractions with Higher-Order Functions)、1.3.1(Functions as Arguments)、Exercise 1.30の解答を求めてみる。
コード
function sum(term, a, next, b) {
function iter(a, result) {
return a > b ?
result :
iter(next(a), result + term(a));
}
return iter(a, 0);
}
function identity(x) {
return x;
}
function inc(x) {
return x + 1;
}
function square(x) {
return x * x;
}
function add2(x) {
return x + 2;
}
console.log(sum(identity, 1, inc, 10));
console.log(sum(identity, 1, add2, 10));
console.log(sum(identity, 2, add2, 10));
console.log(sum(square, 1, inc, 10));
console.log(sum(square, 1, add2, 10));
console.log(sum(square, 2, add2, 10));
入出力結果(Terminal, Zsh)
% node answer1.30.js
55
25
30
385
165
220
%