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@nkpart
nkpart / fmap.md
Last active December 5, 2024 05:31
fmap . fmap . fmap

fmap . fmap . fmap

Functors and Traversables compose.

You might have seen this statement before. This is how you can take advantage of it.

Composing many fmap calls gives you a function that will drill down into a structure and modify it at a certain depth in that nested structure.

@adam-p
adam-p / Local PR test and merge.md
Last active May 25, 2025 09:33
Testing a pull request, then merging locally; and avoiding TOCTOU

It's not immediately obvious how to pull down the code for a PR and test it locally. But it's pretty easy. (This assumes you have a remote for the main repo named upstream.)

Getting the PR code

  1. Make note of the PR number. For example, Rod's latest is PR #37: Psiphon-Labs/psiphon-tunnel-core#37

  2. Fetch the PR's pseudo-branch (or bookmark or rev pointer whatever the word is), and give it a local branch name. Here we'll name it pr37:

$ git fetch upstream pull/37/head:pr37
@pditommaso
pditommaso / gist:2265496
Created March 31, 2012 14:26
Read/write input/output stream of interactive process
import java.io.*;
public class TestProcessIO {
public static boolean isAlive(Process p) {
try {
p.exitValue();
return false;
}
catch (IllegalThreadStateException e) {
@danking
danking / gist:1068185
Created July 6, 2011 19:55
A very simple example showing how to use Racket's lexing and parsing utilities
#lang racket
(require parser-tools/lex
(prefix-in re- parser-tools/lex-sre)
parser-tools/yacc)
(provide (all-defined-out))
(define-tokens a (NUM VAR))
(define-empty-tokens b (+ - EOF LET IN))
(define-lex-trans number
(syntax-rules ()