Here is the screenshot of my Xcode Playground:
As you can see, the str is printed as some("Hello"). This really confuses me as there seems to be no documentation on it.
Dose anyone have a good explanation for this some()?
System info:
swift -version: 4.1.2
Xcode: 9.4.1
This appears to be a quirk in print for this compiler, purely conjecture it may be an artefact of work on changing the semantics of implicitly unwrapped optionals, see Abolish ImplicitlyUnwrappedOptional type.
The type Optional is, stripping to the basics, defined as:
enum Optional<Wrapped>
{
case none
case some(Wrapped)
}
Normally if you print() an enum you do get the literals, here none and some(), however print() normally prints optionals as nil and Optional().
It seems in Xcode 9.4.1 (at least) implicitly unwrapped optionals are being printed as optionals but without the special casing, whereas Xcode 9.2 (at least) prints the unwrapped value as would be expected (because it is implicitly unwrapped).
Maybe there is other interesting behaviour for implicitly unwrapped optionals in 9.4.1. You should test in Xcode 10 Beta and/or report a bug (bugreport.apple.com) in 9.4.1 and see what Apple say.
I'm a bit confused the difference between '~' and '^' in packagist ,
code example in composer.json file:
"require": {
"doctrine/dbal": "^2.6", //this is using '^' symbol
"garygreen/pretty-routes": "~0.0.6" //this is using '~' symbol
},
Can someone explain this for me ?
The ~ operator is best explained by example: ~1.2 is equivalent to >=1.2 <2.0.0, while ~1.2.3 is equivalent to >=1.2.3 <1.3.0. As you can see it is mostly useful for projects respecting semantic versioning. A common usage would be to mark the minimum minor version you depend on, like ~1.2 (which allows anything up to, but not including, 2.0).
The ^ operator behaves very similarly but it sticks closer to semantic versioning, and will always allow non-breaking updates. For example ^1.2.3 is equivalent to >=1.2.3 <2.0.0 as none of the releases until 2.0 should break backwards compatibility. For pre-1.0 versions it also acts with safety in mind and treats ^0.3 as >=0.3.0 <0.4.0.
From: https://getcomposer.org/doc/articles/versions.md#tilde-version-range-
I'm new to Nix and I'm trying to understand the hello derivation given in example.
I can understand the syntax and what is supposed to do, however I don't understand
how the initial arguments (and the especially the perl one_ are fed ?
I mean, who is setting the perl argument before calling this derivation.
Does that mean that perl is a dependency of hello ?
Packages are typically written as set of dependencies -> derivation functions, to be assembled later. The arguments you ask about are fed from pkgs/top-level/all-packages.nix, which holds the set of all packages in Nixpkgs.
When you find the hello's line in all-packages.nix, you'll notice it's using callPackage - it's signature is path to Nix expression -> overrides -> derivation. callPackage loads the path, looks at the function it loaded, and for each arguments provides either value from overrides or, if not given, from the huge set in all-packages.nix.
For a nice description of callPackage see http://lethalman.blogspot.com/2014/09/nix-pill-13-callpackage-design-pattern.html - it's a less condensed explanation, showing how you could have invented callPackage yourself :-).
What is the difference between __stdcall and _stdcal? And what is logic at all by putting variable counter of _ mark?
There is no identifier or keyword named _stdcal. However, the MSVC compiler accepts both _stdcall and __stdcall, one or two underscores.
The single underscore is there because the language specification requires it. Vendor specific identifiers in the global namespace or non-standard keywords must be prefixed by an underscore.
The double underscore is there because a vendor forever loses the battle with programmers that think they should use a leading underscore themselves in their own code. Also present in other non-standard keywords, like __interface and __m128. And in other compilers, like gcc's __attribute__. Clearly you'll want to use the documented version, two underscores.
This is PascalCase: SomeSymbol
This is camelCase: someSymbol
This is snake_case: some_symbol
So my questions is whether there is a widely accepted name for this: some-symbol? It's commonly used in url's.
There isn't really a standard name for this case convention, and there is disagreement over what it should be called.
That said, as of 2019, there is a strong case to be made that kebab-case is winning:
https://trends.google.com/trends/explore?date=all&q=kebab-case,spinal-case,lisp-case,dash-case,caterpillar-case
spinal-case is a distant second, and no other terms have any traction at all.
Additionally, kebab-case has entered the lexicon of several javascript code libraries, e.g.:
https://lodash.com/docs/#kebabCase
https://www.npmjs.com/package/kebab-case
https://v2.vuejs.org/v2/guide/components-props.html#Prop-Casing-camelCase-vs-kebab-case
However, there are still other terms that people use. Lisp has used this convention for decades as described in this Wikipedia entry, so some people have described it as lisp-case. Some other forms I've seen include caterpillar-case, dash-case, and hyphen-case, but none of these is standard.
So the answer to your question is: No, there isn't a single widely-accepted name for this case convention analogous to snake_case or camelCase, which are widely-accepted.
It's referred to as kebab-case. See lodash docs.
It's also sometimes known as caterpillar-case
This is the most famous case and It has many names
kebab-case: It's the name most adopted by official software
caterpillar-case
dash-case
hyphen-case or hyphenated-case
lisp-case
spinal-case
css-case
slug-case
friendly-url-case
As the character (-) is referred to as "hyphen" or "dash", it seems more natural to name this "dash-case", or "hyphen-case" (less frequently used).
As mentioned in Wikipedia, "kebab-case" is also used. Apparently (see answer) this is because the character would look like a skewer... It needs some imagination though.
Used in lodash lib for example.
Recently, "dash-case" was used by
Angular (https://angular.io/guide/glossary#case-types)
NPM modules
https://www.npmjs.com/package/case-dash (removed ?)
https://www.npmjs.com/package/dasherize
Adding the correct link here Kebab Case
which is All lowercase with - separating words.
I've always called it, and heard it be called, 'dashcase.'
There is no standardized name.
Libraries like jquery and lodash refer it as kebab-case. So does Vuejs javascript framework. However, I am not sure whether it's safe to declare that it's referred as kebab-case in javascript world.
I've always known it as kebab-case.
On a funny note, I've heard people call it a SCREAM-KEBAB when all the letters are capitalized.
Kebab Case Warning
I've always liked kebab-case as it seems the most readable when you need whitespace. However, some programs interpret the dash as a minus sign, and it can cause problems as what you think is a name turns into a subtraction operation.
first-second // first minus second?
ten-2 // ten minus two?
Also, some frameworks parse dashes in kebab cased property. For example, GitHub Pages uses Jekyll, and Jekyll parses any dashes it finds in an md file. For example, a file named 2020-1-2-homepage.md on GitHub Pages gets put into a folder structured as \2020\1\2\homepage.html when the site is compiled.
Snake_case vs kebab-case
A safer alternative to kebab-case is snake_case, or SCREAMING_SNAKE_CASE, as underscores cause less confusion when compared to a minus sign.
I'd simply say that it was hyphenated.
Worth to mention from abolish:
https://github.com/tpope/vim-abolish/blob/master/doc/abolish.txt#L152
dash-case or kebab-case
In Salesforce, It is referred as kebab-case. See below
https://developer.salesforce.com/docs/component-library/documentation/lwc/lwc.js_props_names
Here is a more recent discombobulation. Documentation everywhere in angular JS and Pluralsight courses and books on angular, all refer to kebab-case as snake-case, not differentiating between the two.
Its too bad caterpillar-case did not stick because snake_case and caterpillar-case are easily remembered and actually look like what they represent (if you have a good imagination).
My ECMAScript proposal for String.prototype.toKebabCase.
String.prototype.toKebabCase = function () {
return this.valueOf().replace(/-/g, ' ').split('')
.reduce((str, char) => char.toUpperCase() === char ?
`${str} ${char}` :
`${str}${char}`, ''
).replace(/ * /g, ' ').trim().replace(/ /g, '-').toLowerCase();
}
This casing can also be called a "slug", and the process of turning a phrase into it "slugify".
https://hexdocs.pm/slugify/Slug.html