reborg

Rich Already Answered That!

A list of commonly asked questions, design decisions, reasons why Clojure is the way it is as they were answered directly by Rich (even when from many years ago, those answers are pretty much valid today!). Feel free to point friends and colleagues here next time they ask (again). Answers are pasted verbatim (I've made small adjustments for readibility, but never changed a sentence) from mailing lists, articles, chats.

How to use:

• The link in the table of content jumps at the copy of the answer on this page.
• The link on the answer itself points back at the original post.

Table of Content

simonw

{
  page(url:"http://www.eventbrite.com/") {
    title: text(selector:"title")
    cards: query(selector:"div.poster-card") {
      name: text(selector:"[itemprop=name]")
      url: attr(selector:"meta[itemprop=url]", name:"content")
      image_src: attr(selector:".js-poster-image", name:"src")
    }
  }
}

machielg

package  test;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Spliterator;
import java.util.function.Consumer;

import com.datastax.driver.core.ResultSet;
import com.datastax.driver.core.Row;

simonw

import json, datetime

class RoundTripEncoder(json.JSONEncoder):
    DATE_FORMAT = "%Y-%m-%d"
    TIME_FORMAT = "%H:%M:%S"
    def default(self, obj):
        if isinstance(obj, datetime.datetime):
            return {
                "_type": "datetime",
                "value": obj.strftime("%s %s" % (

sorenmacbeth

(defn tokenizer-seq
  "Build a lazy-seq out of a tokenizer with TermAttribute"
  [^TokenStream tokenizer ^TermAttribute term-att]
  (lazy-seq
    (when (.incrementToken tokenizer)
      (cons (.term term-att) (tokenizer-seq tokenizer term-att)))))

(defn load-analyzer [^java.util.Set stopwords]
  (StandardAnalyzer. Version/LUCENE_CURRENT stopwords))

rednaxelafx

The "size" field shows total reserved GC heap size in MB, which includes all generations (including PermGen).
"32-bits Oops" means the shift is zero; otherwise it'd be non-zero.

If UseCompressedOops is false, or if the heap is too big to use compressed oops, then PrintCompressedOopsMode won't print anything. The -Xmx32g example below show that ergonomics didn't set UseCompressedOops to true.

If the heap is too big, HotSpot would print a warning message and set UseCompressedOops to false.

Arachnid

import bisect

class NFA(object):
  EPSILON = object()
  ANY = object()
  
  def __init__(self, start_state):
    self.transitions = {}
    self.final_states = set()
    self._start_state = start_state