So I'm trying to convert this Python function into Javascript. I'm new to Python, so some of the syntax is difficult for me to cipher. Here's both the original code and my attempt at JS-conversion. I know I've interpreted something wrong, because what I have now is an infinite loop.

Python:

graph = [[0,1,0,0,1,0],[1,0,1,0,1,0],[0,1,0,1,0,0],[0,0,1,0,1,1],[1,1,0,1,0,0],[0,0,0,1,0,0]]

def N(vertex):
    c = 0
    l = []
    for i in graph[vertex]:
        if i is 1 :
         l.append(c)
        c+=1
    return l 

def bronk(r,p,x):
    if len(p) == 0 and len(x) == 0:
        print r
        return

    for vertex in p[:]:
        r_new = r[::]
        r_new.append(vertex)
        p_new = [val for val in p if val in N(vertex)] #this and
        x_new = [val for val in x if val in N(vertex)] #this part was particularly difficult to understand 
        bronk(r_new,p_new,x_new)
        p.remove(vertex)
        x.append(vertex)

bronk([], [0,1,2,3,4,5], [])

And here's my attempt at its conversion to JS:

'use strict';
const graph = [[0,1,0,0,1,0],[1,0,1,0,1,0],[0,1,0,1,0,0],[0,0,1,0,1,1],[1,1,0,1,0,0],[0,0,0,1,0,0],];

function N(vertex){
  let c = 0;
  const l = [];
  for (let i in graph[vertex]){
      if (i){
        l.push(c);
        c++;
      }
  }
  return l;
}

function bronk(r,p,x){
  if (p.length == 0 && x.length == 0){
    console.log(r);
    return;
  }
  for (let vertex in p.slice(0)){
    const r_new = r.slice(0);
    r_new.push(vertex);
    const p_new=p.filter(val=>~~N(vertex).indexOf(val)); //here´s my best guess...
    const x_new=x.filter(val=>~~N(vertex).indexOf(val));
    bronk(r_new, p_new, x_new);
    p=p.splice(vertex,1);
    x.push(vertex);
  }
}

bronk([], [0,1,2,3,4,5], []);

I got the Python code from this question.

Edit: I'm working in an ES6 environment.

So I'm trying to convert this Python function into Javascript. I'm new to Python, so some of the syntax is difficult for me to cipher. Here's both the original code and my attempt at JS-conversion. I know I've interpreted something wrong, because what I have now is an infinite loop.

Python:

graph = [[0,1,0,0,1,0],[1,0,1,0,1,0],[0,1,0,1,0,0],[0,0,1,0,1,1],[1,1,0,1,0,0],[0,0,0,1,0,0]]

def N(vertex):
    c = 0
    l = []
    for i in graph[vertex]:
        if i is 1 :
         l.append(c)
        c+=1
    return l 

def bronk(r,p,x):
    if len(p) == 0 and len(x) == 0:
        print r
        return

    for vertex in p[:]:
        r_new = r[::]
        r_new.append(vertex)
        p_new = [val for val in p if val in N(vertex)] #this and
        x_new = [val for val in x if val in N(vertex)] #this part was particularly difficult to understand 
        bronk(r_new,p_new,x_new)
        p.remove(vertex)
        x.append(vertex)

bronk([], [0,1,2,3,4,5], [])

And here's my attempt at its conversion to JS:

'use strict';
const graph = [[0,1,0,0,1,0],[1,0,1,0,1,0],[0,1,0,1,0,0],[0,0,1,0,1,1],[1,1,0,1,0,0],[0,0,0,1,0,0],];

function N(vertex){
  let c = 0;
  const l = [];
  for (let i in graph[vertex]){
      if (i){
        l.push(c);
        c++;
      }
  }
  return l;
}

function bronk(r,p,x){
  if (p.length == 0 && x.length == 0){
    console.log(r);
    return;
  }
  for (let vertex in p.slice(0)){
    const r_new = r.slice(0);
    r_new.push(vertex);
    const p_new=p.filter(val=>~~N(vertex).indexOf(val)); //here´s my best guess...
    const x_new=x.filter(val=>~~N(vertex).indexOf(val));
    bronk(r_new, p_new, x_new);
    p=p.splice(vertex,1);
    x.push(vertex);
  }
}

bronk([], [0,1,2,3,4,5], []);

I got the Python code from this question.

Edit: I'm working in an ES6 environment.

• javascript
• python

Share Improve this question Follow edited May 23, 2017 at 12:13 CommunityBot 111 silver badge asked Dec 10, 2016 at 11:34 OkkuOkku 7,85444 gold badges3232 silver badges4343 bronze badges

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2 Answers 2

Sorted by: Reset to default 4

They're both List prehensions in python

The closest you can get to a list prehension in python in Javascript (Without ES6, babel and its relations) is to use Array.Map (Similar to python's map)

Example in python

>>> l = [2, 4, 6, 8, 10, 12]
>>> [int(i / 2) for i in l]
[1, 2, 3, 4, 5, 6]

In Javascript:

l = [2, 4, 6, 8, 10, 12]
l.map(function(i){ return i / 2 });
[1, 2, 3, 4, 5, 6]

With Arrow functions in ES6, you can get rid of the function(){}

l.map(x => x/2)
[2, 4, 6, 8, 10, 12]

So your code should look like this

const p_new = p.map(function(i){ if(i in N(vertex)){ return i } });
const x_new = x.map(function(i){ if(i in N(vertex)){ return i } });

It would be better to use:

p.filter(val => graph[vertex][val])

As this cuts out the useless Array creation that N does.

Also ~~ doesn't properly convert -1 to false and 0 .. n to true. Use !!~ instead.