JavaScript

2018.02.18

整数と1byte配列の相互変換(ビッグエンディアン)

function p(a){
    console.log(a);
}
function dispArrayLine_hex(a){
    let s = "";
    for(let i=0; i<a.length; i++){
        s += "0x" + a[i].toString(16);
        if(a.length-1 !== i){
            s += ",";
        }
    }
    s = "[" + s + "]";
    p(s);
}
function swap(a, l, r){
    let t = a[l];
    a[l] = a[r];
    a[r] = t;
}
function reverse(a){
    let l = 0;
    let r = a.length-1;
    while(true){
        if(r<=l){
            break;
        }
        swap(a,l,r);
        l++;
        r--;
    }
}
function intToBytes(n){
    let a = [];
    let cnt = 0;
    while(true){
        a[cnt++] = n % 256;
        n = Math.floor(n/256);
        if(0===n){
            break;
        }
    }
    // ビッグエンディアンにする
    reverse(a);
    return a;
}
function bytesToInt(list){
    let n = 0;
    let keta = 1;
    for(let i=list.length-1; 0<=i; i--){
        n += keta * list[i];
        keta *= 256;
    }
    return n;
}

// let n = Number.MAX_SAFE_INTEGER;
let n = 0x123456789abcde;
p(n);
let a = intToBytes(n);
dispArrayLine_hex(a);
let b = bytesToInt(a);
p(b);

function p(a){

console.log(a);

}

function dispArrayLine_hex(a){

let s = "";

for(let i=0; i<a.length; i++){

s += "0x" + a[i].toString(16);

if(a.length-1 !== i){

s += ",";

}

s = "[" + s + "]";

p(s);

}

function swap(a, l, r){

let t = a[l];

a[l] = a[r];

a[r] = t;

}

function reverse(a){

let l = 0;

let r = a.length-1;

while(true){

if(r<=l){

break;

}

swap(a,l,r);

l++;

r--;

}

function intToBytes(n){

let a = [];

let cnt = 0;

while(true){

a[cnt++] = n % 256;

n = Math.floor(n/256);

if(0===n){

break;

}

// ビッグエンディアンにする

reverse(a);

return a;

}

function bytesToInt(list){

let n = 0;

let keta = 1;

for(let i=list.length-1; 0<=i; i--){

n += keta * list[i];

keta *= 256;

}

return n;

}

// let n = Number.MAX_SAFE_INTEGER;

let n = 0x123456789abcde;

p(n);

let a = intToBytes(n);

dispArrayLine_hex(a);

let b = bytesToInt(a);

p(b);

2018.02.08

callback関数は、呼び出し先の関数の中で呼び出される関数

let a = [0,1,2,3,4];

console.log(a);

// コールバック関数
let f = (v,i,a) => {
    v = v * v;
    console.log(v);
};

a.forEach(f);

console.log(a);

let a = [0,1,2,3,4];

console.log(a);

// コールバック関数

let f = (v,i,a) => {

v = v * v;

console.log(v);

};

a.forEach(f);

console.log(a);

2018.02.07

JavaScriptでクイックソート

ES6ではデフォルト引数が使えるらしいけれど、
とりあえずデフォルト引数は使わずに実装。

let a = [];
let len = 20;
for(let i=0; i<len; i++){
    a[i] = len-i;
}
dispArrayLine(a);
quicksort(a);
dispArrayLine(a);

function quicksort(a){
    let left = 0;
    let right = a.length-1;
    quicksort_core(a,left,right);
}
function quicksort_core(a, left, right){
    if(right<=left){
        return;
    }
    let l = left;
    let r = right;
    let p = getPivot(a[l], a[l+1], a[r]);
    while(true){
        while(a[l]<p){
            l++;
        }
        while(p<a[r]){
            r--;
        }
        if(r<=l){
            break;
        }
        swap(a,l,r);
        l++;
        r--;
    }
    quicksort_core(a,left,l-1);
    quicksort_core(a,r+1,right);
}
function getPivot(a,b,c){
    if(a>b){
        if(b>c){
            return b;
        }else{
            return a>c ? c:a;
        }
    }else{
        if(a>c){
            return a;
        }else{
            return b>c ? c:b;
        }
    }
}
function swap(a, l, r){
    let t = a[l];
    a[l] = a[r];
    a[r] = t;
}
function p(arg){
    console.log(arg);
}
function dispArrayList(a){
    for(let k in a){
        let v = a[k];
        p(k + " => " + v);
    }
}
function dispArrayLine(a){
    let s = "";
    for(let k in a){
        let v = a[k];
        s += v + " ";
    }
    s = s.trim();
    p(s);
}

let a = [];

let len = 20;

for(let i=0; i<len; i++){

a[i] = len-i;

}

dispArrayLine(a);

quicksort(a);

dispArrayLine(a);

function quicksort(a){

let left = 0;

let right = a.length-1;

quicksort_core(a,left,right);

}

function quicksort_core(a, left, right){

if(right<=left){

return;

}

let l = left;

let r = right;

let p = getPivot(a[l], a[l+1], a[r]);

while(true){

while(a[l]<p){

l++;

}

while(p<a[r]){

r--;

}

if(r<=l){

break;

}

swap(a,l,r);

l++;

r--;

}

quicksort_core(a,left,l-1);

quicksort_core(a,r+1,right);

}

function getPivot(a,b,c){

if(a>b){

if(b>c){

return b;

}else{

return a>c ? c:a;

}

}else{

if(a>c){

return a;

}else{

return b>c ? c:b;

}

function swap(a, l, r){

let t = a[l];

a[l] = a[r];

a[r] = t;

}

function p(arg){

console.log(arg);

}

function dispArrayList(a){

for(let k in a){

let v = a[k];

p(k + " => " + v);

}

function dispArrayLine(a){

let s = "";

for(let k in a){

let v = a[k];

s += v + " ";

}

s = s.trim();

p(s);

}

2018.02.07

JavaScript(ECMAScript2015, ES6)の練習

ついにJavaScriptを勉強する必要が出てきた。
とりあえず試運転。

let a = [];
let min_randomInt = 2.4;
let max_randomInt = 7.2;
let times = 10000;

for(let i=0; i<times; i++){
    let n = getRandomInt(min_randomInt, max_randomInt);
    if(isUndefined(a[n])){
        a[n] = 1;
    }else{
        a[n] += 1;
    }
}

dispArrayList(a);

// library
function p(arg){
    console.log(arg);
}
function getRandomInt(min, max){
    min = Math.ceil(min);
    max = Math.floor(max);
    let randomOffset = Math.floor(Math.random()*(max-min+1));
    return min + randomOffset;
}
function isUndefined(arg){
    return (undefined === arg);
}
function dispArrayList(a){
    for(let k in a){
        let v = a[k];
        p(k + " => " + v);
    }
}

let a = [];

let min_randomInt = 2.4;

let max_randomInt = 7.2;

let times = 10000;

for(let i=0; i<times; i++){

let n = getRandomInt(min_randomInt, max_randomInt);

if(isUndefined(a[n])){

a[n] = 1;

}else{

a[n] += 1;

}

dispArrayList(a);

// library

function p(arg){

console.log(arg);

}

function getRandomInt(min, max){

min = Math.ceil(min);

max = Math.floor(max);

let randomOffset = Math.floor(Math.random()*(max-min+1));

return min + randomOffset;

}

function isUndefined(arg){

return (undefined === arg);

}

function dispArrayList(a){

for(let k in a){

let v = a[k];

p(k + " => " + v);

}

8 9 10 1112

JavaScript

整数と1byte配列の相互変換(ビッグエンディアン)

callback関数は、呼び出し先の関数の中で呼び出される関数

JavaScriptでクイックソート

JavaScript(ECMAScript2015, ES6)の練習

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