Building Abstractions with Functions - Functions and the Processes They Generate - Example: Testing for Primality - Probabilistic methods - smallest divisor, Date.now, performance.now
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)、1.2(Functions and the Processes They Generate)、1.2.6(Example: Testing for Primality)、Probabilistic methods、Exercise 1.22の解答を求めてみる。
コード
function square(x) {
return x * x;
}
function display(x) {
console.log(x);
}
function get_time() {
// return Date.now();
return performance.now();
}
function smallest_divisor(n) {
return find_divisor(n, 2);
}
function find_divisor(n, test_divisor) {
return square(test_divisor) > n ?
n :
divides(test_divisor, n) ?
test_divisor :
find_divisor(n, test_divisor + 1);
}
function divides(a, b) {
return b % a === 0;
}
function is_prime(n) {
return n === smallest_divisor(n);
}
function timed_prime_test(n) {
display(n);
return start_prime_test(n, get_time());
}
function start_prime_test(n, start_time) {
return is_prime(n) ?
report_prime(get_time() - start_time) :
true;
}
function report_prime(elapsed_time) {
display(" *** ");
display(`${String(elapsed_time)}`);
}
function search_for_primes(start, stop) {
function iter(n) {
n > stop ?
true :
f(n);
}
function f(n) {
timed_prime_test(n);
iter(n + 2);
}
start % 2 === 0 ?
iter(start + 1) :
iter(start);
}
search_for_primes(1001, 1019);
search_for_primes(10001, 10039)
search_for_primes(100001, 100043);
search_for_primes(1000001, 1000039);
入出力結果(Terminal, Zsh)
% node answer1.22.js
1001
1003
1005
1007
1009
***
0.0050780028104782104
1011
1013
***
0.00479300320148468
1015
1017
1019
***
0.00474199652671814
10001
10003
10005
10007
***
0.007089003920555115
10009
***
0.020183995366096497
10011
10013
10015
10017
10019
10021
10023
10025
10027
10029
10031
10033
10035
10037
***
0.006496995687484741
10039
***
0.007244989275932312
100001
100003
***
0.02151799201965332
100005
100007
100009
100011
100013
100015
100017
100019
***
0.018776997923851013
100021
100023
100025
100027
100029
100031
100033
100035
100037
100039
100041
100043
***
0.018588006496429443
1000001
1000003
***
0.11717100441455841
1000005
1000007
1000009
1000011
1000013
1000015
1000017
1000019
1000021
1000023
1000025
1000027
1000029
1000031
1000033
***
0.058589011430740356
1000035
1000037
***
0.05999299883842468
1000039
***
0.0666009932756424
%