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<title>Mu</title
t">a>: <p> <div style='font-style: italic; margin-left:2em'> Is it a language, or an operating system, or a virtual machine? <p> Mu. </div> Read these first: <a href='http://akkartik.name/about'>problem statement</a>, <a href='http://github.com/akkartik/mu#readme'>readme and installation instructions</a> (mu requires minimal dependencies). <p> Mu's code looks quite alien, requiring editors to be specially configured to colorize it in a sane manner. So this page provides links to the source files showing how it currently looks in my <a href='https://github.com/akkartik/mu/blob/master/mu.vim'>custom setup</a>. <p>Whetting your appetite: some example programs. <ul> <li><a href='html/x.mu.html'>x.mu</a>: a simple program to add two numbers together. Shows that at bottom mu is a simple VM bytecode designed to convert directly to machine code. <li><a href='html/factorial.mu.html'>factorial.mu</a>: everyone's favorite example, showing how mu supports conditionals and loops without any special syntax, using the special labels '{' and '}'. <li><a href='html/tangle.mu.html'>tangle.mu</a>: another (contrived) version of factorial showing mu's ability to 'tangle' code from multiple places into a single function or 'recipe'. <li><a href='html/counters.mu.html'>counters.mu</a>: lexical scope <li><a href='html/callcc.mu.html'>callcc.mu</a>: first-class continuations. Mu also supports first-class functions and delimited continuations. <li>simple examples showing off support for concurrency: <a href='html/fork.mu.html'>fork.mu</a>, <a href='html/channel.mu.html'>channel.mu</a> <li>simple examples showing off hardware control: <a href='html/display.mu.html'>display.mu</a>, <a href='html/keyboard.mu.html'>keyboard.mu</a>. <li><a href='html/screen.mu.html'>screen.mu</a>: example program showing print primitives that inject a screen <em>dependency</em> which can be faked for testing. <li><a href='html/chessboard.mu.html'>chessboard.mu</a>: putting it all together, the big kahuna: a complete console program along with thorough tests of its behavior including both screen and keyboard handling. </ul> <p><b>Part I</b>: basic infrastructure <p/><a href='html/000organization.cc.html'>000organization.cc</a>: the basic skeleton program. Compiles and runs but doesn't do much. Later <em>layers</em> hook into this skeleton to add functionality. Mu's guarantee: you can <a href='http://youtube.com/watch?v=c8N72t7aScY'>load features</a> up until any layer, and it will compile and pass all tests until that point. <a href='http://akkartik.name/post/wart-layers'>More details &rarr;</a> <br/><a href='html/001help.cc.html'>001help.cc</a>: just a simple test layer to show how to hook into the skeleton. Also summarizes how to invoke mu, behaviors that later layers will be providing. <br/><a href='html/002test.cc.html'>002test.cc</a>: mu's minimalist test harness, relying on a couple of one-liners in the makefile to autogenerate lists of tests to run. <br/><a href='html/003trace.cc.html'>003trace.cc</a>: support for logging facts about our program, and for <a href='http://akkartik.name/post/tracing-tests'>checking the facts logged in tests</a>. (<a href='html/003trace.test.cc.html'>tests for the test harness</a>) <p><b>Part II</b>: the mu virtual machine, designed to compile easily to machine language. <p/><a href='html/010vm.cc.html'>010vm.cc</a>: core data structures: recipes (functions), instructions and reagents (operands). <br/><a href='html/011load.cc.html'>011load.cc</a>: the textual representation of recipes and how it's turned into the data structures. <br/><a href='html/012transform.cc.html'>012transform.cc</a>: after mu programs are loaded but before they are run they can be transformed in an extensible manner akin to lisp macros. Think of this as the core of mu's &lsquo;compiler&rsquo; for providing high-level features atop the core. <br/><a href='html/013literal_string.cc.html'>013literal_string.cc</a>: extend the loader to support literal strings in various instructions. <br/><a href='html/014literal_noninteger.cc.html'>014literal_noninteger.cc</a>: extend the loader to support non-integer numbers. <br/><a href='html/020run.cc.html'>020run.cc</a>: executing mu recipes by executing the list of instructions they contain. <br/>Various primitive operations: on <a href='html/021arithmetic.cc.html'>numbers</a>, <a href='html/022boolean.cc.html'>booleans</a>, for <a href='html/023jump.cc.html'>control flow</a>, and <a href='html/024compare.cc.html'>comparing values</a>. <br/>Primitive operations to help with testing: <a href='html/025trace.cc.html'>tracing/logging</a>, <a href='html/026assert.cc.html'>assert</a> and <a href='html/027debug.cc.html'>debug by print</a>. <br/><a href='html/030container.cc.html'>030container.cc</a>: compound types akin to records, structs or classes. <br/><a href='html/031address.cc.html'>031address.cc</a>: adding and removing layers of indirection to mu data. <br/><a href='html/032array.cc.html'>032array.cc</a>: all mu data structures are <a href='html/033length.cc.html'>bounds-checked</a>. <br/><a href='html/034exclusive_container.cc.html'>034exclusive_container.cc</a>: tagged unions or sum types. <br/><a href='html/035call.cc.html'>035call.cc</a>: calls to recipes look just like primitive operations. <br/><a href='html/036call_ingredient.cc.html'>036call_ingredient.cc</a>: how recipes pass arguments or 'ingredients' without introducing any syntax and breaking the metaphor of recipes as lists of instructions. <br/><a href='html/037call_reply.cc.html'>037call_reply.cc</a>: recipes can return arbitrary numbers of values to their callers. <br/><a href='html/038scheduler.cc.html'>038scheduler.cc</a>: running multiple recipes concurrently using <em>routines</em> that might execute in interleaved fashion. <br/><a href='html/039wait.cc.html'>039wait.cc</a>: primitives for synchronization between routines. <p><b>Part III</b>: transforms to provide 80% of the benefits of high-level languages. <br/><a href='html/040brace.cc.html'>040brace.cc</a>: how mu provides structured goto-less programming without introducing the syntax of conditionals and loops other languages require. <br/><a href='html/041name.cc.html'>041name.cc</a>: how mu transforms variable names to raw memory addresses. <br/><a href='html/042new.cc.html'>042new.cc</a>: rudimentary memory allocator that is aware of all global types in any mu program. <br/><a href='html/043space.cc.html'>043space.cc</a>: how variables in different routines are isolated from each other using <em>spaces</em>. Mu &lsquo;local variables&rsquo; are allocated on the heap. <br/><a href='html/044space_surround.cc.html'>044space_surround.cc</a>: Chaining spaces together to accomodate variables with varying lifetimes and ownership properties. <br/><a href='html/045closure_name.cc.html'>045closure_name.cc</a>: how spaces can implement lexical scope. <br/><a href='html/046tangle.cc.html'>046tangle.cc</a>: support for layers in mu programs. They've been so good to us. <br/><a href='html/047jump_label.cc.html'>047jump_label.cc</a>: since we have <br/><a href='html/048call_variable.cc.html'>048call_variable.cc</a>: higher-order functions. <br/><a href='html/049continuation.cc.html'>049continuation.cc</a>: first-class and delimited continuations, primitives for yield, exceptions and much else besides. <br/><a href='html/050scenario.cc.html'>050scenario.cc</a>: mu's first syntax &mdash; not for code but for tests. (<a href='html/051scenario_test.mu.html'>example</a>) <p><b>Part IV</b>: beginnings of a standard library <p/><a href='html/060string.mu.html'>060string.mu</a>: bounds-checked rather than null-terminated. Unicode-aware. <br/><a href='html/061channel.mu.html'>061channel.mu</a>: channels are mu's only synchronization primitive, queues that can cause the routine reading or writing from them to stall without taking up CPU resources. <br/><a href='html/062array.mu.html'>062array.mu</a> <br/><a href='html/063list.mu.html'>063list.mu</a> <br/><a href='html/064random.cc.html'>064random.cc</a> <p><b>Part V</b>: Nascent tools for browsing mu codebases, and for teaching programming to non-programmers by getting them hooked on the value of tests. The eventual goal is <b>an environment that watches the programmers try out the code they write, and turns the interactive sessions into reproducible test scenarios.</b> <p/><a href='html/070display.cc.html'>070display.cc</a>: primitives for using the keyboard and screen. <br/><a href='html/071print.mu.html'>071print.mu</a>: helpers that can swap the real screen with fake ones for testing. <br/><a href='html/072scenario_screen.cc.html'>072scenario_screen.cc</a>: writing tests that check what is printed to screen. (<a href='html/073scenario_screen_test.mu.html'>examples</a>) <br/><a href='html/074keyboard.mu.html'>074keyboard.mu</a>: helpers that can swap the real keyboard with fake ones for testing. <br/><a href='html/075scenario_keyboard.cc.html'>075scenario_keyboard.cc</a>: writing tests using a fake keyboard. (<a href='html/076scenario_keyboard_test.mu.html'>examples</a>) <br/><a href='html/077trace_browser.cc.html'>077trace_browser.cc</a>: a zoomable UI for inspecting traces generated by mu programs. Allows both scanning a high-level view and drilling down into selective details. <p/><a href='html/999spaces.cc.html'>Epilogue</a>: maps summarizing various address spaces, and the conventions that regulate their use in previous layers. <hr> <p> The zen of mu: <ul> <li>traces, not interfaces</li> <li>be rewrite-friendly, not backwards-compatible</li> <li>be easy to port rather than portable</li> <li>global structure matters more than local hygiene</li> </ul> <p> Mu's vision of utopia: <ul> <li>1/1000th the code to run your devices <li>1000x the number of forks for open source projects <li>make simple changes to large open-source codebases in an afternoon (but don't worry about merging them upstream) <li>large codebases that don't slow down with age, that continue to evolve just as fast as when they were first started. <li>software that rewards curiosity, allowing anyone to query its design decisions and easily try out radical redesign ideas in a sandbox. Learning programming as needed. <li><a href='https://www.dreamsongs.com/Files/PatternsOfSoftware.pdf'>habitable</a>digital environments <li>a <em>literate</em> digital society with widespread skills to comprehend large-scale software structure and compare-and-contrast programs in a domain. (I don't think anybody is literate by this definition today.) <p style='margin-bottom: 2em'/>