var a=[4,1,2,7]

var b = [] ;
for (var i=0;i<a.length;i++){b.push(2 * a[i])}

console.log(b);   // [8,2,4,14]



//for i in a: print(i)

//for i in range(0, len(a)): print(a[i])

//(f x y)
//f(x,y)

var b = [];
for(var i=0;i<a.length;i++){b.push(a[i],a[i])};


console.log(b); // [4,4,1,1,2,2,7,7]

b=[];
for(var i=a.length-1;i>=0;i--){b.push(a[i])};


console.log(b); // [7,2,1,4]

//lisp lots of irritating stupid parentheses

a=[-5,7,1,8,3,-2];
b=[];
for (var  i=0;i<a.length;i++) {
    if (a[i]>=0) {b.push(a[i])}
};

console.log(b) // [7,1,8,3]

//[1,2,3,4]


//[3,2,1]
function rev (ar) {
    var b = [];
    for(var i=0;i<ar.length;i++) {
        b.unshift(ar[i])
    }
    return b
}


console.log(rev ([1,6,8,8,3,3,9]));

function fac(n) {
    var fac=1;
    for(var i=n;i>=1;i--) {
        fac*=i;
    }
    return fac;
}

console.log(fac(5));

//snake_case
//snake-case-in-lisp
//CamelCase
//dromedaryCase - pascalCase



function r_fac(n) {
    if (n === 0) {
        return 1;
    } else {
      return n * fac(n-1);
   }
}

console.log(r_fac(10));

function fub(n) {
    if (n===0) {
        return 1;
    }else if (n===1) {
        return 2;
    } else {
        return fub(n-1)+fub(n-2);
    }
}

console.log(fub(4));

function r_rev(ar) {
    if (0 === ar.length) {
        return []
    } else {
        return r_rev(ar.slice(1)).concat([ar[0]]);

    }
}

console.log(r_rev([1,2,3]));

function r_rev(ar) {
    return (0 === ar.length) ? [] : r_rev(ar.slice(1)).concat([ar[0]]);
}
console.log(r_rev([1,2,3]));

//r_rev([1,2,3])=>[3,2,1]
//r_rev([2,3])=>co


//r_rev([1,2,3]) = r_rev([2,3]).concat([1]) = r_rev([3]).concat([2]).concat([1]) = r_rev([]).concat([3]).concat([2]).concat([1])

//усл ? ветка1 : ветка2

function max(ar) {
    var res = ar[0];
    for(i=1;i<ar.length;i++) {
        if (ar[i]>res){
            res=ar[i]
        }
    }
    return res
}

function max(ar) {
    if (1 === ar.length){
        return ar[0]
    }else {
       let num = max(ar.slice(1));
       if (ar[0]>num) {
           return ar[0]
       }else{
           return num
       }
    }
}


console.log(max([1,23,54,67,4566,344,3456,7888]));

function is_sorted(ar) {
    for (var i=0;i<(ar.length-1);i++) {
        if (ar[i]>ar[i+1]) {
            return false
        }
    }
    return true
}

function is_sorted(ar) {
    if (ar.length === 0) {
        return true
    }else if (ar[1]>ar[2]) {
        return false
    }else {
        return is_sorted(ar.slice(1))
    }
}



console.log(is_sorted([1,2,3,4,5]));
console.log(is_sorted([1,2,3,4,0]))



//[7,9,12]
//[8,5,12]

function bubble_sort(ar) {
    while (! is_sorted(ar)) {
        for (var i=0;i<ar.length-1;i++) {
          if (ar[i]>ar[i+1]) {
              let num = ar[i];
              ar[i]=ar[i+1];
              ar[i+1]=num
            }
        }
    }
    return ar
}


console.log(bubble_sort([1,2,4,3,2,1,2,3,5,6,7,5]));


//do {..} while (...)

function bubble_sort(ar) {
    do {
        var flag = true;
        for (var i=0;i<ar.length-1;i++) {
          if (ar[i]>ar[i+1]) {
              let num = ar[i];
              ar[i]=ar[i+1];
              ar[i+1]=num
              flag = false
            }
        }
    }while (! flag)
    return ar
}

bubble_sort([1,2,2,1,3,4,3,2,5,3,6,6]);

//[4,2,3,21,2,5,7,4,5,6] =>
//[2,3]            [2,3]
//[21,5,7,4,5,6]   [4,5,5,6,7,21]

function qsort(ar) {
    if (ar.length === 0) {
        return []
    }else {
        let lesser = [];
        let greater = [];
        for (var i=1;i<ar.length;i++) {
            if (ar[i]< ar[0]) {
                lesser.push(ar[i])
            }else{
                greater.push(ar[i])
            }
        }
        return qsort(lesser).concat(ar[0]).concat(qsort(greater))
    }
}

function my_qsort(ar) {
    if (ar.length === 0) {
        return []
    }else {
        return my_qsort(ar.slice(1).filter(x=>x<ar[0])).concat(ar[0]).concat(my_qsort(ar.slice(1).filter(x=>x>=ar[0])))
    }
}

console.log(my_qsort([14,13,76,52,98,71]));