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create table foo (
  id bigserial primary key,
  prev bigint
);

insert into foo(id, prev) values
  (1, NULL),
  (2, 1),
  (4, 2),
  (12, 4),

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#!/bin/bash

regexp='^[-+]?[0-9]*(\.[0-9]*)?$'
validateNumber() {
	if [[ $1 == *[0-9]* && $1 =~ $regexp ]]; then
		echo "$1"
	else
		printf >&2 '%s is not a valid number\n' "$1"
	fi
}

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/**
This middleware enhances redux-thunk, to deal with asynchronous actions

conventions and usage:
- an action is a plain object `{type: TYPE_CONSTANT, value: ANY_VALUE}` or an array of those actions (handled by reducer)
- you can shape action creators as `queryArgs => promise` (where the promise returns an action)
- or `queryArgs => action` (where the action value is a promise).

examples:
  const getProfile = id => ({ type: GET_PROFILE, value: fetchApi(`/profile/${id}`) });

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import { graphql } from 'react-apollo';
import gql from 'graphql-tag';

const TodoApp = ({ loading, error, data: { todos, refetch }, ...props }) => {
    if (loading) return <p>Loading...</p>;
    if (error) return <p>Error :(</p>;
    return (
        <div {...props}>
            <button onClick={() => refetch()}>Refresh</button>
            <ul>{todos && todos.map(todo => <li key={todo.id}>{todo.text}</li>)}</ul>

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import React from 'react';

/**
 * Simple HOC, taking a fetcher function (returning a promise) then a Component
 * @returns Component accepting a ({ data, error, loading }) => {..} function as children
 */

export default fetcher => Component =>
	class extends React.PureComponent {
		state = { loading: true, data: [], error: undefined };

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const DIR = os.homedir() + '/.foo';

// adapted from  https://stackoverflow.com/a/24977085/3183756
const downloadFromFs = (req, res) => {
  const { name } = req.params;
  const filePath = path.join(DIR, name);
  fs.stat(filePath, (err, stats) => {
    if (err) {
      if (err.code === 'ENOENT') {
        // 404 Error if file not found

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// ## like \1 but named:
/(?<fruit>apple|fig)==\k<fruit>/u.test('fig==fig')
// true


// ## named group captures:
'we can'.replace(/(?<subject>\w+) (?<verb>\w+)/u, '$<subject>...$<verb>')
//"we...can"

'yes, we can'.replace(/(?<w>\w+)[,\s]+/gu, '$<w>...')

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export default class BetterMap {
  constructor(data) {
    this.m = new Map(Array.isArray(data) || data instanceof Map ? data : Object.entries(data));
  }
  set(k, v) { // return BetterMap
    this.m.set(k, v);
    return new SortableMap(this.m);
  }
  delete(k) { // return BetterMap
    this.m.delete(k, v);

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• dom builder examples https://jsfiddle.net/crl/tfo58xmt/5/ https://jsfiddle.net/crl/7jo9zp5t/22/
• like <input type="search"> but not https://jsfiddle.net/364Lbu1w/3/
• contenteditable https://jsfiddle.net/crl/eumxoudn/39/ react https://jsfiddle.net/crl/eumxoudn/11/
• designs address form | list | checkbox | increment buttons /5 | button | dropdown | circle nav
• fps-meter https://output.jsbin.com/banewul/
• play with unicodes https://jsfiddle.net/crl/s0xbrwv5/10/, golden ratio https://jsfiddle.net/crl/bveyL2uf/6/
• slot machine https://jsfiddle.net/crl/sbh0hrfu/
• canvas vs svg https://jsfiddle.net/crl/vbtbm83k/17/
• cancellable fetch https://jsfiddle.net/crl/8ns0abst/6/

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mapTo: 428.186ms
mapTo2: 319.058ms
ord: 348.390ms
mapToMany: 786.141ms
mapToMany2: 780.661ms
ord agg: 31856.442ms