mirror of
https://github.com/enso-org/enso.git
synced 2024-11-23 08:08:34 +03:00
b7a8909818
- Improved performance by batching simulatenous node edits, including metadata updates when dragging many selected nodes together. - Updated Vue to new version, allowing us to use `defineModel`. - Fixed #9161 - Unified all handling of auto-blur by making `useAutoBlur` cheap to register - all logic goes through a single window event handler. - Combined all `ResizeObserver`s into one. - Fixed the behaviour of repeated toast messages. Now only the latest compilation status is visible at any given time, and the errors disappear once compilation passes. - Actually fixed broken interaction of node and visualization widths. There no longer is a style feedback loop and the visible node backdrop width no longer jumps or randomly fails to update.
179 lines
7.0 KiB
Markdown
179 lines
7.0 KiB
Markdown
---
|
|
layout: developer-doc
|
|
title: Literals
|
|
category: syntax
|
|
tags: [syntax, literals]
|
|
order: 5
|
|
---
|
|
|
|
# Literals
|
|
|
|
Enso supports a small set of literals that allow the expression of some common
|
|
types in literal form in the source code.
|
|
|
|
<!-- MarkdownTOC levels="2,3" autolink="true" -->
|
|
|
|
- [Numeric Literals](#numeric-literals)
|
|
- [Text Literals](#text-literals)
|
|
- [Inline Text Literals](#inline-text-literals)
|
|
- [Text Block Literals](#text-block-literals)
|
|
- [Inline Block Literals](#inline-block-literals)
|
|
- [Escape Sequences](#escape-sequences)
|
|
- [Vector Literals](#vector-literals)
|
|
|
|
<!-- /MarkdownTOC -->
|
|
|
|
## Numeric Literals
|
|
|
|
Enso provides rich support for numeric literals, including literals that use
|
|
different numeric bases. It does, of course, support floating point numerals as
|
|
well.
|
|
|
|
A numeric literal takes the form:
|
|
|
|
```ebnf
|
|
digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;
|
|
hex = "a" | "b" | "c" | "d" | "e" | "f";
|
|
number-digit = digit | hex;
|
|
decimal-point = ".";
|
|
|
|
float-digit = number-digit | decimal-point;
|
|
|
|
base-specifier = { digit };
|
|
|
|
numeric-literal = [base-specifier, "_"], { number-digit };
|
|
```
|
|
|
|
If no base is specified, it is inferred to be a standard base-10 numeral.
|
|
|
|
Some examples of numeric literals follow:
|
|
|
|
```ruby
|
|
decimal = 12345.39
|
|
decimal_explicit = 10_1029301
|
|
octal = 8_122137
|
|
hex = 16_ae2f14
|
|
binary = 2_10011101010
|
|
```
|
|
|
|
> Actionables for this section are:
|
|
>
|
|
> - Think about whether we want to support explicit fractional and complex
|
|
> literals, or whether these should be relegated to type constructors.
|
|
|
|
## Text Literals
|
|
|
|
Enso provides rich support for textual literals in the language, supporting both
|
|
raw and interpolated strings natively.
|
|
|
|
- **Raw Strings:** Raw strings are delimited using the standard double-quote
|
|
character (`"`). Raw strings don't support any escape sequences.
|
|
|
|
```ruby
|
|
raw_string = "Hello, world!"
|
|
```
|
|
|
|
- **Interpolated Strings:** Interpolated strings support the splicing of
|
|
executable Enso expressions into the string. Such strings are delimited using
|
|
the single-quote (`'`) character, and splices are delimited using the backtick
|
|
(`` ` ``) character. Splices are run, and then the result is converted to a
|
|
string using `show`. These strings also have support for all kinds of
|
|
[escape sequences](#escape-sequences).
|
|
|
|
```ruby
|
|
fmt_string = 'Hello, my age is `time.now.year - person.birthday.year`'
|
|
```
|
|
|
|
### Inline Text Literals
|
|
|
|
In Enso, inline text literals are opened and closed using the corresponding
|
|
quote type for the literal. They may contain escape sequences but may _not_ be
|
|
broken across lines.
|
|
|
|
```ruby
|
|
inline_raw = "Foo bar baz"
|
|
inline_interpolated = 'Foo `bar` baz'
|
|
```
|
|
|
|
### Text Block Literals
|
|
|
|
In Enso, text block literals rely on _layout_ to determine the end of the block,
|
|
allowing users to only _open_ the literal. Block literals are opened with three
|
|
of the relevant quote type, and the contents of the block are determined by the
|
|
following layout rules:
|
|
|
|
- The first child line of the block sets the baseline left margin for the block.
|
|
Any indentation up to this margin will be removed.
|
|
- Any indentation further than this baseline will be retained as part of the
|
|
text literal.
|
|
- The literal is _closed_ by the first line with a _lower_ level of indentation
|
|
than the first child line and will not contain the final blank line.
|
|
|
|
```
|
|
block_raw = '''
|
|
part of the string
|
|
still part of the string
|
|
|
|
also part of the string
|
|
|
|
not_string_expr = foo bar
|
|
```
|
|
|
|
### Inline Block Literals
|
|
|
|
In order to easily transition between using text blocks and single-line
|
|
literals, we allow for defining an inline block literal. This is a literal that
|
|
uses the same start delimiter as a block literal (see above), but rather than
|
|
ending the literal through de-indenting from the block's level of indentation,
|
|
the literal is ended upon the line ending.
|
|
|
|
```
|
|
inline_block =
|
|
"""this is all part of the literal
|
|
but_this_is_not
|
|
```
|
|
|
|
### Escape Sequences
|
|
|
|
Format literals in Enso support many kinds of escape sequence. These are
|
|
described below.
|
|
|
|
| Name | Escape Sequence | Unicode | Notes |
|
|
| :----------- | :-------------: | :--------: | :---------------------------------------------------------------------------------------- |
|
|
| Byte Escape | `\x##` | `U+00##` | 8-bit character specification. |
|
|
| U16 Escape | `\u####` | `U+####` | 16-bit unicode character, where each `#` is a hex digit. |
|
|
| U21 Escape | `\u{######}` | `U+######` | 21-bit unicode character, where `######` is 1-6 hex digits. |
|
|
| U32 Escape | `\U########` | `U+######` | 32-bit unicode character, where each `#` is a hex digit and the first two bytes are `00`. |
|
|
| Null | `\0` | `U+0000` | The null character. |
|
|
| Alert | `\a` | `U+0007` | The bell/alert character. |
|
|
| Backspace | `\b` | `U+0008` | The backspace character. |
|
|
| Form Feed | `\f` | `U+000C` | The form-feed character. |
|
|
| LF | `\n` | `U+000A` | The line-feed character (newline on unix systems). |
|
|
| CR | `\r` | `U+000D` | The carriage return character (part of newline on windows systems). |
|
|
| Tab | `\t` | `U+0009` | The horizontal tab character. |
|
|
| Vertical Tab | `\v` | `U+000B` | The vertical tab character. |
|
|
| Backslash | `\\` | `U+005C` | A literal backslash character. |
|
|
| Double Quote | `\"` | `U+0022` | A literal double quote character. |
|
|
| Single Quote | `\'` | `U+0027` | A literal single quote character. |
|
|
| Backtick | `` \` `` | `U+0060` | A literal backtick character. |
|
|
|
|
The only one of the above escape sequences that is supported in a raw text
|
|
literal is `\"`. All other occurrences of `\` in such literals are treated as a
|
|
literal backslash.
|
|
|
|
## Vector Literals
|
|
|
|
Enso also supports vector literals, which allow users to create literal vectors
|
|
of elements.
|
|
|
|
```ruby
|
|
literal = [elem_1, elem_2, elem_3, ...]
|
|
```
|
|
|
|
A vector literal works as follows:
|
|
|
|
- It is begun by the `[` character.
|
|
- It is ended by the `]` character.
|
|
- Elements in vector literals are concatenated using the `,` operator, which
|
|
acts as `cons` on vectors.
|