Parser Reference

Syntax

Murex supports both expressions and statements. You can use the interchangeably with your code and the Murex parser will decide whether to run that code as an expression or statement.

Expressions

Expressions are patterns formed like equations (eg $val = 1 + 2).

Strings must be quoted in expressions.

Statements

Statements are traditional shell command calls (eg command parameters...).

Quoting strings is optional in statements.

Not all operators are supported in statements.

Order Of Operations

Expressions and statements are split by pipes and terminators. Each statement and expression is executed from left to right, with the statement or expression parsed by the following rules of operation

Order of operations:

1. expression or statement discovery
2. sub-shells / sub-expressions
3. multiplication / division (expressions only)
4. addition / subtraction (expressions only)
5. comparisons, eg greater than
6. logical and (sub-expressions only)
7. logical or (sub-expressions only)
8. elvis (expressions only)
9. assign (expressions only)
10. left to right

Expression Or Statement Discovery

First a command is read as an expression. Because the rules of parsing expressions are stricter than statements, everything is assumed to be an expression unless the expression parser fails, which then it is assumed to be a statement.

Operators And Tokens

Terminology

• left: this is the value to the left hand side of the operator
• right: this is the value to the right hand side of the operator

Example: left operator right

Modifiers

All modifiers replace the left, operator and right with the returned value of the modifier.

All returns will be num data type (or their original type if strict types is enabled).

Modifiers are only supported in expressions.

Operator	Name	Operation
*	Multiplication	Multiply left by right
/	Divide	Divide left by right
+	Addition	Add left with right
-	Subtraction	Subtract left by right

Read more:

• Data types: num, int, float
• Strict types config: strict types
• Operators: +, -, *, /

Comparators

All comparators replace the left, operator and right with the returned value of the comparator.

All returns will be bool data type, either true or false.

Comparators are only supported in expressions.

Operator	Name	Operation
>	Greater Than	true if left is greater than right
>=	Greater Or Equal To	true if left is greater or equal to right
<	Less Than	true if left is less than right
<=	Less Or Equal To	true if left is less or equal to right
==	Equal To	true if left is equal to right
!=	Not Equal To	false if left is equal to right
~~	Like	true if left string is like right string
!!	Not Like	false if left string is like right string
=~	Matches Regexp	true if left matches regexp pattern on right
!~	Does Not Match Regexp	false if left matches regexp pattern on right

Read more:

• Data types: bool

Assignment

Assignment returns true if successful.

Assignment is only supported in expressions.

Operator	Name	Operation
=	Assign (overwrite)	Assign right to left
:=	Assign (retain)	EXPERIMENTAL
<~	Assign Or Merge	Merge right (array / object) into left
+=	Assign And Add	Add right to left and assign to left
-=	Assign And Subtract	Subtract right from left and assign to left
*=	Assign And Multiply	Multiply right with left and assign to left
/=	Assign And Divide	Divide right with left and assign to left

Read more:

• Data types: bool
• Operators: =, <~, +=, -=, =, =

Conditionals

Conditionals replace left, operator and right with the value defined in operation.

These conditionals are only supported in expressions.

Operator	Name	Operation
??	Null Coalescence	Returns left if not null, otherwise right
?:	Elvis	Returns left if truthy, otherwise right

Read more:

• Operators: ??, ?:

Sigils

Sigils are special prefixes that provide hints to the parser.

Sigils are supported in both expressions and statements.

Token	Name	Operation
$	Scalar	Expand value as a string
@	Array	Expand value as an array
~	Home	Expand value as the persons home directory
%	Builder	Create an array, map or nestable string

Constants

Constants are supported in both expressions and statements. However null, true, false and number will all be interpreted as strings in statements.

Token	Name	Operation
null	Null	null (null / nil / void) type
true	True	bool (boolean) true
false	False	bool (boolean) false
number	Number	num (numeric) value
'string'	String Literal	str (string) literal value
"string"	Infix String	str (string) value, supports escaping & infixing
%(string)	String Builder	Creates a nestable str (string)
%[array]	Array Builder	Creates a json (JSON) array (list)
%{map}	Object Builder	Creates a json (JSON) object (map / dictionary)

Read more:

• Operators: 'string', "string", %(string), %[array], %{map}

Sub-shells

Sub-shells are a way of inlining expressions or statements into an existing expression or statement. Because of this they are supported in both.

Syntax	Name	Operation
command( parameters... )	C-Style Functions	Inline a command as a function
${command parameters...}	Sub-shell (scalar)	Inline a command line as a string
@{command parameters...}	Sub-shell (array)	expand a command line as an array
(expression)	Sub-expression	Inline an expression (statement)
(expression)	Sub-expression	Order of evaluation (expression)

Read more:

• C-style functions, sub-shells, sub-expressions

Boolean Operations

Boolean operators behave like pipes.

They are supported in both expressions and statements.

Operator	Name	Operation
&&	And	Evaluates right if left is truthy
||	Or	Evaluates right if left is falsy

Pipes

Pipes always flow from left to right.

They are supported in both expressions and statements.

Operator	Name	Operation
|	POSIX Pipe	POSIX compatibility
->	Arrow Pipe	Context aware pipe
=>	Generic Pipe	Convert stdout to * (generic) then pipe
|>	Truncate File	Write stdout to file, overwriting contents
>>	Append File	Write stdout to file, appending contents

Terminators

"LF" refers to the life feed character, which is a new line.

Token	Name	Operation
;	Semi-Colon	End of statement or expression (optional)
LF	Line Feed	End of statement or expression (new line)

Escape Codes

Any character can be escaped via \ to signal it isn't a token. However some characters have special meanings when escaped.

"LF" refers to the life feed character, which is a new line.

Token	Name	Operation
\s	Space	Same as a space character
\t	Tab	Same as a tab character
\r	Carriage Return	Carriage Return (CR) sometimes precedes LF
\n	Line Feed	Line Feed (LF), typically a new line
\LF	Escaped Line Feed	Statement continues on next line

Other Reference Material

Language Guides

1. Language Tour, which is an introduction into the Murex language.

2. Rosetta Stone, which is a reference table comparing Bash syntax to Murex's.

3. Builtins, for docs on the core builtins.

Murex's Source Code

The parser is located Murex's source under the lang/ path of the project files.

Pages

• ( expression ): Inline expressions
• C-style functions: Inlined commands for expressions and statements
• "Double Quote": Initiates or terminates a string (variables expanded)
• $Variable Sigil: Expand values as a scalar
• %(Brace Quote): Initiates or terminates a string (variables expanded)
• %[] Array Builder: Quickly generate arrays
• %{} Object Builder: Quickly generate objects (dictionaries / maps)
• && And Logical Operator: Continues next operation if previous operation passes
• 'Single Quote': Initiates or terminates a string (variables not expanded)
• (brace quote): Write a string to the STDOUT without new line (deprecated)
• *= Multiply By Operator: Multiplies a variable by the right hand value (expression)
• * Multiplication Operator: Multiplies one numeric value with another (expression)
• += Add With Operator: Adds the right hand value to a variable (expression)
• + Addition Operator: Adds two numeric values together (expression)
• -= Subtract By Operator: Subtracts a variable by the right hand value (expression)
• -> Arrow Pipe: Pipes STDOUT from the left hand command to STDIN of the right hand command
• - Subtraction Operator: Subtracts one numeric value from another (expression)
• /= Divide By Operator: Divides a variable by the right hand value (expression)
• / Division Operator: Divides one numeric value from another (expression)
• <~ Assign Or Merge: Merges the right hand value to a variable on the left hand side (expression)
• => Generic Pipe: Pipes a reformatted STDOUT stream from the left hand command to STDIN of the right hand command
• = (arithmetic evaluation): Evaluate a mathematical function (deprecated)
• >> Append File: Writes STDIN to disk - appending contents if file already exists
• >> Append Pipe: Redirects STDOUT to a file and append its contents
• ?: Elvis Operator: Returns the right operand if the left operand is falsy (expression)
• ?? Null Coalescing Operator: Returns the right operand if the left operand is empty / undefined (expression)
• ? STDERR Pipe: Pipes STDERR from the left hand command to STDIN of the right hand command (DEPRECATED)
• @Array Sigil: Expand values as an array
• [ ..Range ]: Outputs a ranged subset of data from STDIN
• [ Index ]: Outputs an element from an array, map or table
• [[ Element ]]: Outputs an element from a nested structure
• [{ Lambda }]: Iterate through structured data
• { Curly Brace }: Initiates or terminates a code block
• |> Truncate File: Writes STDIN to disk - overwriting contents if file already exists
• | POSIX Pipe: Pipes STDOUT from the left hand command to STDIN of the right hand command
• || Or Logical Operator: Continues next operation only if previous operation fails
• ~ Home Sigil: Home directory path variable