Melody is a language designed to compile to and maintain a 1-1 relationship with regular expressions, while being more readable and maintainable.

The current goal is supporting the JavaScript implementation of regular expressions.

⚠️ Melody is very new and is unstable at the moment ⚠️

Examples

Note: these are for the currently supported syntax and may change

Batman Theme

16 of "na";

2 of match {
  <space>;
  "batman";
}

// 🦇🦸‍♂️

Turns into

/(?:na){16}(?:\sbatman){2}/

Twitter Hashtag

"#";
some of <word>;

// #melody

Turns into

/#\w+/

Introductory Courses

some of <word>;
<space>;
"1";
2 of <digit>;

// classname 1xx

Turns into

/\w+\s1\d{2}/

Indented Code (2 spaces)

some of match {
  2 of <space>;
}

some of <char>;
";";

//  let value = 5;

Turns into

/(?:\s{2})+.+;/

Semantic Versions

<start>;

option of "v";

capture major {
  some of <digit>;
}

".";

capture minor {
  some of <digit>;
}

".";

capture patch {
  some of <digit>;
}

<end>;

Turns into

/^v?(?<major>\d+)\.(?<minor>\d+)\.(?<patch>\d+)$/

Playground

You can try Melody in your browser using the playground

Documentation

Read the documentation here

Install

Cargo

cargo install melody_cli

From Source

git clone https://github.com/yoav-lavi/melody.git
cd melody
cargo install --path crates/melody_cli

CLI Usage

melody [OPTIONS] [PATH]

OPTIONS:
  -f, --file <FILE>    write to an output file
  -r, --repl           starts the melody REPL
  -n, --no-color       print output with no color
  -V, --version        print version information
  -h, --help           print help information

Keywords

• of - used after a number or a range and before a sequence to be matched, e.g. 5 of "A";, equivalent to regex {5}
• to - used to create a range (either as a quantifier or as a character range), e.g. 5 to 9, equivalent to regex {5,9} if before an of or [5-9] otherwise
• capture - used to open a capture or named capture block, equivalent to regex (...)
• match - used to open a match block, equivalent to regex (?:...)
• some - used with of to express 1 or more of a pattern, equivalent to regex +
• over - used with of to express more than an amount of a pattern, equivalent to regex {6,} (assuming over 5 of ...)
• option - used with of to express 0 or 1 of a pattern, equivalent to regex ?
• either - used to open an either block, equivalent to regex (...|...)
• any - used with of to express 0 or more of a pattern, equivalent to regex *

Symbols

• <start> - matches the start of the string, equivalent to regex ^
• <end> - matches the end of the string, equivalent to regex $
• <char> - matches a single character, equivalent to regex .
• <space> - equivalent to regex \s
• not <space> - equivalent to regex \S
• <newline> - equivalent to regex \n
• <tab> - equivalent to regex \t
• <return> - equivalent to regex \r
• <feed> - equivalent to regex \f
• <null> - equivalent to regex \0
• <digit> - equivalent to regex \d
• not <digit> - equivalent to regex \D
• <vertical> - equivalent to regex \v
• <word> - equivalent to regex \w
• not <word> - equivalent to regex \W

Literals

• "..." or '...' - used to mark a literal part of the match. Melody will automatically escape characters as needed. Quotes (of the same kind surrounding the literal) should be escaped

Raw

• `...`; - added directly to the output without any escaping

Extras

• // - used to mark comments

File Extension

The Melody file extension is .mdy

Crates

• melody_compiler - The Melody compiler 📦 📖
• melody_cli - A CLI wrapping the Melody compiler 📦 📖
• melody_wasm - WASM binding for the Melody compiler

Extensions

• VSCode

Feature Status

✅ - Implemented

🐣 - Partially implemented

❌ - Not implemented

❓ - Unclear whether this will be implemented

❔ - Unclear what the syntax will be

Melody	Regex	Status
5 of "hello";	(?:hello){5}	✅
5 to 7 of "A";	A{5,7}	✅
capture { ... }	(...)	✅
capture name { ... }	(?<name>...)	✅
match { ... }	(?:...)	✅
<space>;	\s	✅
A to Z;	[A-Z]	✅
a to z;	[a-z]	✅
0 to 9;	[0-9]	✅
// comment		✅
start;	^	✅
end;	$	✅
<newline>;	\n	✅
<tab>;	\t	✅
<return>;	\r	✅
<feed>;	\f	✅
<null>;	\0	✅
<digit>;	\d	✅
<vertical>;	\v	✅
<word>;	\w	✅
"..."; (literal)	...	✅
'...'; (literal)	...	✅
<code>\...` (raw)	...	✅
'\'';	'	✅
"\"";	"	✅
<code>\\\	`	✅
support non alphanumeric characters		✅
output to file		✅
no color output		✅
<char>	.	✅
some of	+	✅
syntax highlighting extension		✅
over 5 of "A";	A{6,}	✅
not <digit>;	\D	✅
not <space>;	\S	✅
not <word>;	\W	✅
WASM binding		✅
Rust crate		✅
option of	?	✅
any of	*	✅
either { ...; ...; }	(...|...)	✅
tests		✅
auto escape for literals		✅
enforce group close		❌
<backspace>	[\b]	❌
file watcher		❌
nested groups	(...(...))	❌
multiple ranges	[a-zA-Z0-9]	❌
general cleanup and modules		❌
TS / JS build step		❌
more robust parsing mechanism (ast)		❌
ahead { ... }	(?=...)	❌
behind { ... }	(?<=...)	❌
not ahead { ... }	(?!...)	❌
not behind { ... }	(?<!...)	❌
not "A";	[^A]	❔
flags: global, multiline, ...	/.../gm...	❔
/* comment */		❔
any of "a", "b", "c"	[abc]	❔
(?)	*?	❔
(?)	\#	❔
(?)	\k<name>	❔
(?)	\p{...}	❔
(?)	\P{...}	❔
(?)	\uYYYY	❔
(?)	\xYY	❔
(?)	\ddd	❔
(?)	\cY	❔
(?)	\b	❔
(?)	\B	❔
(?)	$1	❔
(?)	$`	❔
(?)	$&	❔
(?)	x20	❔
(?)	x{06fa}	❔
variables / macros		❓
regex optimization		❓
standard library / patterns		❓
reverse compiler		❓