If you start from the node-app/hello-express project template, Glitch will run the project with pnpm install --shamefully-flatten && npm start, and the sample code hosts the static index.html via Express through a random forwarded port. Changes to Javascript and HTML files will automatically trigger a rerun of npm start, while changes to the package.json will also rerun pnpm install.
The "watch" key itself has three potential keys in it. "install" and "start" describe the files to watch and trigger a rerun of the commands in those keys above. Each should each contain an object with "include" and "exclude" keys, which contain arrays of strings, each string being a regex pattern matching a possible filename(s). Whenever a file changes that is matched by the include key, it will rerun the appropriate command (start or install), unless the file also matches one of the patterns in exclude.
Quick update here, but @potch has written a little guide that helps clarify some useful stuff to know for configuring Glitch projects, especially those in other languages: !/glitchnomicon?path=README.md:1:0
Could someone give a very simple example demonstrating how and when glitches can occur when using RX and show on the same example how and why the corresponding ReactFX solution is glitch free.
In the context of FRP, a glitch is a temporary inconsistency in the dataflow graph. Due to the fact that updates do not happen instantaneously, but instead take time to compute, the values within an FRP system may be transiently out of sync during the update process. Furthermore, depending on the nature of the FRP system, it is possible to have nodes be updated more than once in a propagation.
First note that ReactFX is not "glitch free" out of the box, but it gives you tools to eliminate glitches. Unless you take some conscious effort to use them, ReactFX is not more glitch-free than RX (e.g. rxJava).
The techniques to eliminate glitches in ReactFX rely on the fact that event propagation is synchronous. On the other hand, event propagation in RX is always asynchronous, thus these techniques cannot be implemented in an RX system.
The reason is simple: a.CombineLatest(b, f) will react when either a or b produces a value, combining this new value and the last observed value of the other observable. This is by design, but from my experience, people using RX sometimes consider these to be glitches, especially when coming from other FRP libraries that have a different notion of "latest".
A glitch is a short-lived fault in a system, such as a transient fault that corrects itself, making it difficult to troubleshoot. The term is particularly common in the computing and electronics industries, in circuit bending, as well as among players of video games. More generally, all types of systems including human organizations and nature experience glitches.
A glitch, which is slight and often temporary, differs from a more serious bug which is a genuine functionality-breaking problem. Alex Pieschel, writing for Arcade Review, said: "'bug' is often cast as the weightier and more blameworthy pejorative, while 'glitch' suggests something more mysterious and unknowable inflicted by surprise inputs or stuff outside the realm of code".[1] The word itself is sometimes humorously described as being short for "gremlins lurking in the computer hardware".[2]
Some reference books, including Random House's American Slang, claim that the term comes from the German word glitschen 'to slip' and the Yiddish word glitshn 'to slide, to skid'. Either way, it is a relatively new term. It was first widely defined for the American people by Bennett Cerf on the June 20, 1965, episode of What's My Line as "a kink ... when anything goes wrong down there [Cape Kennedy], they say there's been a slight glitch". The astronaut John Glenn explained the term in his section of the book Into Orbit, writing that
Another term we adopted to describe some of our problems was "glitch". Literally, a glitch is a spike or change in voltage in an electrical circuit which takes place when the circuit suddenly has a new load put on it. You have probably noticed a dimming of lights in your home when you turn a switch or start the dryer or the television set. Normally, these changes in voltage are protected by fuses. A glitch, however, is such a minute change in voltage that no fuse could protect against it.[3]
According to a Wall Street Journal article written by Ben Zimmer,[6] The Yale law librarian Fred Shapiro came up with the new earliest use of the word yet found: May 19, 1940. That was when the novelist Katharine Brush wrote about glitch in her column "Out of My Mind" (syndicated in The Washington Post, The Boston Globe, and other papers). Brush corroborated Tony Randall's radio recollection:
Other examples from the world of radio can be found in the 1940s. The April 11, 1943, issue of The Washington Post carried a review of Helen Sioussat's book about radio broadcasting, Mikes Don't Bite. The reviewer noted an error and wrote, "In the lingo of radio, has Miss Sioussat pulled a 'muff,' 'fluff,' 'bust,' or 'glitch'?" And in a 1948 book called The Advertising and Business Side of Radio, Ned Midgley explained how a radio station's "traffic department" was responsible for properly scheduling items in a broadcast. "Usually most 'glitches,' as on-the-air mistakes are called, can be traced to a mistake on the part of the traffic department", Midgley wrote.
Further digging reveals that in the 1950s, glitch made the transition from radio to television. In a 1953 ad in Broadcasting magazine, RCA boasted that their TV camera has "no more a-c power line 'glitches' (horizontal-bar interference)". And Bell Telephone ran an ad in a 1955 issue of Billboard showing two technicians monitoring the TV signals that were broadcast on Bell System lines: "When he talks of 'glitch' with a fellow technician, he means a low frequency interference which appears as a narrow horizontal bar moving vertically through the picture".
A 1959 article in Sponsor, a trade magazine for television and radio advertisers, gave another technical usage in an article about editing TV commercials by splicing tape. "'Glitch' is slang for the 'momentary jiggle' that occurs at the editing point if the sync pulses don't match exactly in the splice". It also provided one of the earliest etymologies of the word, noting that, "'Glitch' probably comes from a German or Yiddish word meaning a slide, a glide or a slip".[citation needed]
An electronics glitch or logic hazard is a transition that occurs on a signal before the signal settles to its intended value, particularly in a digital circuit. Generally, this implies an electrical pulse of short duration, often due to a race condition between two signals derived from a common source but with different delays. In some cases, such as a well-timed synchronous circuit, this could be a harmless and well-tolerated effect that occurs normally in a design. In other contexts, a glitch can represent an undesirable result of a fault or design error that can produce a malfunction. Some electronic components, such as flip-flops, are triggered by a pulse that must not be shorter than a specified minimum duration in order to function correctly; a pulse shorter than the specified minimum may be called a glitch. A related concept is the runt pulse, a pulse whose amplitude is smaller than the minimum level specified for correct operation, and a spike, a short pulse similar to a glitch but often caused by ringing or crosstalk.
A computer glitch is the failure of a system, usually containing a computing device, to complete its functions or to perform them properly. It frequently refers to an error which is not detected at the time it occurs but shows up later in data errors or incorrect human decisions. Situations which are frequently called computer glitches are incorrectly written software (software bugs), incorrect instructions given by the operator (operator errors, and a failure to account for this possibility might also be considered a software bug), undetected invalid input data (this might also be considered a software bug), undetected communications errors, computer viruses, Trojan attacks and computer exploiting (sometimes called "hacking").
Such glitches could produce problems such as keyboard malfunction, number key failures, screen abnormalities (turned left, right or upside-down), random program malfunctions, and abnormal program registering.
Examples of computer glitches causing disruption include an unexpected shutdown of a water filtration plant in New Canaan, 2010,[7] failures in the Computer Aided Dispatch system used by the police in Austin, resulting in unresponded 911 calls,[8] and an unexpected bit flip causing the Cassini spacecraft to enter "safe mode" in November 2010.[9] Glitches can also be costly: in 2015, a bank was unable to raise interest rates for weeks resulting in losses of more than a million dollars per day.[10]
Glitches may include incorrectly displayed graphics, collision detection errors, game freezes/crashes, sound errors, and other issues. Graphical glitches are especially notorious in platforming games, where malformed textures can directly affect gameplay (for example, by displaying a ground texture where the code calls for an area that should damage the character, or by not displaying a wall texture where there should be one, resulting in an invisible wall). Some glitches are potentially dangerous to the game's stored data, such as MissingNo. from the Pokmon games.[12]
"Glitching" is the practice of players exploiting faults in a video game's programming to achieve tasks that give them an unfair advantage in the game, over NPC's or other players, such as running through walls or defying the game's physics. Glitches can be deliberately induced in certain home video game consoles by manipulating the game medium, such as tilting a ROM cartridge to disconnect one or more connections along the edge connector and interrupt part of the flow of data between the cartridge and the console.[13] This can result in graphic, music, or gameplay errors. Doing this, however, carries the risk of crashing the game or even causing permanent damage to the game medium.[14]
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