[swift-evolution] [Pitch] Extending Swift Literals

Daniel Steinberg daniel at dimsumthinking.com
Mon Jul 11 06:57:51 CDT 2016

Perhaps I’m not thinking about literals correctly. I don’t think of them as something I can create in code using this syntax. I think of literals as something that I have a literal representation of. I can drag a color into Xcode or a playground. Same with an image.

In your proposal, I can imagine dragging in a URL from Safari or a webview or a sound file. I would support those two being added.

The geometry elements don’t seem to be in the same category of “thing”. Although I agree that Points and Rects can be a pain to construct, I can’t imagine what I’m dragging and dropping. If instead you want to use the literal syntax to construct one, then I’m definitely against this as that feels like a return to a stringly world in which we create things without compiler help.



> On Jul 10, 2016, at 11:48 PM, Erica Sadun via swift-evolution <swift-evolution at swift.org> wrote:
> This is purely additive and would not be eligible for Swift 3. 
> gist: https://gist.github.com/erica/c92f6ab115af89d5c4b9161487df6a3c <https://gist.github.com/erica/c92f6ab115af89d5c4b9161487df6a3c>
> -- E
> Extending Swift Literals
> Proposal: TBD
> Author: Erica Sadun <http://github.com/erica>
> Status: TBD
> Review manager: TBD
>  <https://gist.github.com/erica/c92f6ab115af89d5c4b9161487df6a3c#introduction>Introduction
> This proposal expands Swift's language literals to include common cross-platform concepts that need not require.
>  <https://gist.github.com/erica/c92f6ab115af89d5c4b9161487df6a3c#motivation>Motivation
> A Swift literal represents a fixed value in source code. A literal can be a string, a number (for example an integer), a compound value (such as an array), or one of several predefined "playground" literals including colors, resource file paths, and resource images.
> Swift literals do not have types. They are universal representations that are evaluated and their types inferred from the context in which they are used. Because their nature is typeless, the same color literal can initialize UIColor, NSColor, and SKColor instances. The type cannot be inferred from the source without the context of its destination.
> let color = #colorLiteral(red: 0.8100712299, green: 0.1511939615, blue: 0.4035313427, alpha: 1)
>  <https://gist.github.com/erica/c92f6ab115af89d5c4b9161487df6a3c#detailed-design>Detailed Design
> Namespace redesign
> Kind	Literal	Parameters
> Color	`#literal.color(red:, green:, blue:, alpha:)`	floating point values
> Image	`#literal.image(resourceName:)`	String with resource name
> File	`#literal.file(resourceName:)`	String with resource name
> General
> Kind	Literal	Parameters
> Sound	`#literal.audio(resourceName:)`	String with resource name
> URL	`#literal.url(string:)`, `#literal.url(filePath:)`	String with resource location
> Font	`#literal.font(face:, size:)`	string, floating point
> Date	`#literal.date(timeInterval:)`	floating point offset from Unix epoch
> Unicode	`#literal.unicode(name:)`	Official unicode name, e.g. `#literal.unicode(name:"DOG FACE")`
> Geometry
> Kind	Literal	Parameters
> Point	`#literal.point(x:, y:)`, `#literal.point(x:, y:, z:)`, `#literal.point(x:, y:, z:, w:)`	floating point values
> Vector	`#literal.vector(dx:, dy:)`, `#literal.vector(dx:, dy:, dz:)`, `#literal.vector(dx:, dy:, dz:, dw:)`	floating point
> Size	`#literal.size(width:, height:)`, `#literal.size(width:, height:, depth:)` 	floating point
> Rect	`#literal.rect(x:, y:, width:, height:)`	floating point
> Affine Transform	`#literal.affineTransform(a:,b:,c:,d:,tx:,ty:)`, `#literal.affineTransform(translateX:, translateY:)`, `#literal.affineTransform(scaleY:, scaleY:)`, `#literal.affineTransform(rotation:)`, 	floating point
> Bezier Path	`#literal.bezier("M92.21,24.29H75L73,17a8.32,8.32, 0,0,0-8.27-6.74H34.55A7.69,7.69,0,0,0,27,16.6l-2.08 4z")`	String with SVG path notation
>  <https://gist.github.com/erica/c92f6ab115af89d5c4b9161487df6a3c#not-included>Not included:
> Attributed Strings: I would like to see a way to define attributed strings (using some system like CSS/HTML) but could not think up a simple representation similar to the others mentioned in the preceding table.
> JSON Literals: Again, probably too complex and possibly not worth their weight. If they could exist, they'd have to be imported via a resource or URL and transformed to a local type.
>  <https://gist.github.com/erica/c92f6ab115af89d5c4b9161487df6a3c#impact-on-existing-code>Impact on Existing Code
> This proposal is purely additive.
>  <https://gist.github.com/erica/c92f6ab115af89d5c4b9161487df6a3c#alternatives-considered>Alternatives Considered
> Using distinct literal names without subsuming them into a namespaced umbrella.
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