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posted at

C++を使いながらHaskell学習

備忘録も兼ねて ٩(ˊᗜˋ*)و.

配列の中の数を足す

hairetsuplus.cpp
#include<iostream>
#include<vector>
using namespace std;

int main(){
    vector<int> xs{1,2,3};
    vector<int> ys;
    for(auto x:xs){
        ys.emplace_back(x+10);
    }

    for(auto y:ys){
        cout<<y<<endl;
    }
}

11
12
13

hairetsuplus.hs
main = print $ map(+10)[1,2,3]

[11,12,13]

配列の合計値を算出

wa.cpp
#include<iostream>
#include<vector>
using namespace std;

int main(){
    vector<int> xs{1,2,3};
    int total = 0;
    for(auto x:xs){
        total += x;
    }
    cout<<total<<endl;
}

6

wa.hs
main = print $ foldr (+) 0 [1,2,3]

6

配列のある数字以上の数を取り出す

bignumberinsert.cpp
#include<iostream>
#include<vector>
using namespace std;

int main(){
    vector<int> xs{1,2,3,4,5,6};
    vector<int> ys;
    for(auto x:xs){
        if(x>3){
            ys.emplace_back(x);
        }
    }   

    for(auto y:ys){
        cout<<y<<endl;
    }
}

4
5
6

bignumberinsert.hs
main = print $ filter(>3)[1,2,3,4,5,6]

[4,5,6]

関数をかけあわせる

kansuu.cpp
#include<iostream>
#include<vector>
using namespace std;

int f(int x){return x+10;}

int g(int x){return x*x;}

int main(){
    vector<int>xs{1,2,3};
    vector<int>ys;
    for(auto x:xs){
        ys.emplace_back(g(f(x)));
    }

    for(auto y:ys){
        cout<<y<<endl;
    }
}

121
144
169

kansuu.hs
f x = x+10

g x = x * x

main = print $ map(g.f)[1,2,3]

[121,144,169]

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Help us understand the problem. What are the problem?