Michael Bishop cleverca22

attrset ? "key" and attrset.key or fallback have nearly equal complexity costs

if attrset ? "key" then attrset.key else fallback is slightly more expensive,

due to being 3 AST nodes (an ExprIf with an ExprOpHasAttr as the condition and then an ExprSelect to extract the "key")

attrset.key or fallback is slightly cheaper, since it is a single AST node (just ExprSelect)

	/*
	* Copyright (c) 2025 Michael Bishop
	*
	* Permission is hereby granted, free of charge, to any person obtaining
	* a copy of this software and associated documentation files
	* (the "Software"), to deal in the Software without restriction,
	* including without limitation the rights to use, copy, modify, merge,
	* publish, distribute, sublicense, and/or sell copies of the Software,
	* and to permit persons to whom the Software is furnished to do so,
	* subject to the following conditions:

	{ pkgs ? import <nixpkgs> {} }:

	with pkgs;

	let
	inherit (lib) optional optionals;

	erlang = pkgs.beam.interpreters.erlangR24;
	elixir = pkgs.beam.packages.erlangR24.elixir_1_13;
	nodejs = pkgs.nodejs-18_x;

	{-# LANGUAGE OverloadedStrings #-}
	module Escrow where

	import Language.Marlowe.Extended

	main :: IO ()
	main = print . pretty $ contract

	-- We can set explicitRefunds True to run Close refund analysis
	-- but we get a shorter contract if we set it to False

	import System.Exit (exitWith, ExitCode(ExitSuccess))
	import Graphics.UI.GLUT

	main = do
	(progName, _args) <- getArgsAndInitialize
	initialDisplayMode $= [ SingleBuffered, RGBMode ]
	initialWindowSize $= Size 500 500
	_ <- createWindow progName
	exitWith ExitSuccess

	{ stdenv, fetchurl, gfortran }:

	stdenv.mkDerivation rec {
	name = "blas-${version}";
	version = "3.8.0";

	src = fetchurl {
	url = "http://www.netlib.org/blas/${name}.tgz";
	sha256 = "1s24iry5197pskml4iygasw196bdhplj0jmbsb9jhabcjqj2mpsm";
	};

	{ pkgs ? import ./nix/nixpkgs.nix {} }:

	with pkgs;

	haskellPackages.extend (self: super: {
	polysemy = self.callHackageDirect {
	pkg = "polysemy";
	ver = "1.1.0.0";
	sha256 = "1krbhfs6sr9m6nxhs9ygkblwd85w234hll5g7ndzhdwy5pfbyfvm";
	} {};

	self: super:
	let
	pythonOverlay = pself: psuper:
	{
	sundials_3_lapack = pself.callPackage ./pkgs/sundials { };
	myScikits-odes = pself.callPackage ./pkgs/scikits-odes { };
	};
	in {
	pythonPackages = super.pythonPackages.override { overrides = pythonOverlay; };
	}

	# in rails project

	with (import <nixpkgs> {});

	let
	rubyenv = bundlerEnv {
	name = "cart-env";
	# Setup for ruby gems using bundix generated gemset.nix
	inherit ruby_2_6;
	gemfile = ./Gemfile;

	nix-repl> eval = import <nixpkgs/nixos> { configuration = ./snmpd.nix; }
	nix-repl> eval.config.systemd.units."snmpd.service".unit
	«derivation /nix/store/q8nq58244hw0v04w400kzwllxwb42zrg-unit-snmpd.service.drv»