Provided by: muon-meson_0.3.0-4_amd64 
NAME
meson.build - a build system dsl
DESCRIPTION
The meson dsl is a dynamically typed language, similar to other interpreted languages like python and
ruby. All objects are immutable. Functions cannot be defined, only built-in functions are available.
• STRUCTURE - overview of source and project layout
• TYPES - information on all primitive types
• SYNTAX - description of syntax and keywords
STRUCTURE
All meson projects must have a file called `meson.build` at the project root. This is the root build
file. This file must have a call to the `project()` function as its first statement. Additional
`meson.build` files may reside in any subdirectories of the project. These build files are then executed
with the `subdir()` function.
TYPES
The meson build system dsl contains most of the common types that would be expected:
• booleans (written as `true` and `false`)
• integers
• strings
• arrays
• dictionaries
Booleans
Booleans are either `true` or `false`.
OPERATORS
• `and` - logical and
• `or` - logical or
• `not` - logical and
Integers
You can specify an integer literal using decimal, hexadecimal, octal, and binary.
int_1 = 1
int_42 = 42
int_255 = 0xFF
int_493 = 0o755
int_1365 = 0b10101010101
All common arithmetic operations are implemented for integers: addition, subtraction, division,
multiplication, and modulo.
OPERATORS
• `*` - multiplication
• `/` - integer division
• `%` - modulo (remainder)
• `+` - addition
• `-` - subtraction
• `==` - equal to
• `!=` - not equal to
• `<` - less than
• `>` - greater than
• `<=` - less than or equal to
• `>=` - greater than or equal to
Strings
Strings in Meson are declared with single quotes. `` is the escape character.
The full list of escape sequences is:
• `\` Backslash
• `'` Single quote
• `a` Bell
• `b` Backspace
• `f` Formfeed
• `n` Newline
• `r` Carriage Return
• `t` Horizontal Tab
• `v` Vertical Tab
• `ooo` Character with octal value ooo, up to 3 digits long
• `xhh` Character with hex value hh
• `uxxxx` Character with 16-bit hex value xxxx
• `Uxxxxxxxx` Character with 32-bit hex value xxxxxxxx
• `N{name}` Character named name in Unicode database
Multi-line strings are surrounded by 3 consecutive quotes. These are raw strings that do not support the
escape sequences listed above.
Format strings are expressed by a placing leading `f` before the first opening quote. Inside of a format
string, sequences of the form `@[a-z_]+@` will be substituted with the value of the matching variable.
This variable can be of type bool, int, or str.
name = 'Alice'
# prints "Hello Alice"
message(f'Hello @name@')
OPERATORS
• `+` - concatenate two strings
• `/` - concatenate two strings as if `join_paths()` was called
• `[int]` - access the character at index
• `<str> in <str>` - check if str is a substring
• `<str> not in <str>` - check if str is not a substring
• `==` - equal to
• `!=` - not equal to
Arrays
Arrays are delimited by brackets. An array can contain an arbitrary number of objects of any type.
OPERATORS
• `+` - If the rhs operand is an array, it will be joined to the lhs array. If it is a scalar, it will
be appended to the lhs array.
• `[int]` - access the object at index
• `<any> in <array>` - check if object is in `array`
• `<any> not in <array>` - check if object is not in `array`
• `==` - equal to
• `!=` - not equal to
Dictionaries
Dictionaries are delimited by curly braces. A dictionary can contain an arbitrary number of key: value
pairs. Keys are required to be strings, but values can be objects of any type. Dictionaries are
immutable and do not have a guaranteed order.
OPERATORS
• `+` - merge two dictionaries. In case of a conflicting key, the value from the rhs dictionary will
be taken.
• `[str]` - access the object with key `key`
• `<str> in <dict>` - check if key is in `dict`
• `<str> not in <dict>` - check if key is not in `dict`
• `==` - equal to
• `!=` - not equal to
SYNTAX
A meson build file is composed of statements, which are terminated by newlines. Other than the statement-
terminating newline, white space has no syntactic meaning.
Comments
A comment starts with the `#` character and extends until the end of the line.
Variables
A variable can contain a value of any type, and does not need to be predeclared.
var1 = 'hello'
var2 = 102
One important difference in how variables work in the dsl is that all objects are immutable. When you see
an operation which appears like a mutation, actually a new object is created and assigned to the name.
var1 = [1, 2, 3]
var2 = var1
var2 += [4]
# var2 is now [1, 2, 3, 4]
# var1 is still [1, 2, 3]
Function and method calls
Builtin functions are called by their name followed by parenthesis containing optional, comma-separated
arguments. Arguments are either positional or keyword. Keyword arguments are expressed using the
keyword without quotes, followed by a colon.
foo()
foo('bar')
foo('bar', baz: true)
Method calls are expressed by a `.` followed by the same function call syntax as above.
foo.bar()
foo.bar('baz', qux: false)
For a complete list of functions and methods, please see `meson-reference(3)`.
If statements
Start an if statement with the `if` keyword followed by a boolean expression. Further conditions can be
expressed using the `elif` keyword followed by a boolean expression. The `else` keyword can be used to
handle the case when no conditions are matched. An if statement is terminated with the `endif` keyword.
if conditon1
...
elif condition2
...
else condition3
...
endif
Foreach statements
To loop over values in an iterable, use the `foreach` keyword followed by a comma separated list of names
to assign the values of the iterable to, a colon, and an iterable expression. Only arrays and
dictionaries are iterable. A foreach statement is terminated with the `endforeach` keyword.
Arrays have one value to assign to.
foreach value : array
foo(value)
endforeach
Dictionaries have one two values to assign to.
foreach key, value : dictionary
foo(key)
bar(value)
endforeach
Inside a `foreach` block you may use the `break` and `continue` keywords. `break` exits the loop
immediately. `continue` skips the rest of the current iteration.
SEE ALSO
meson-reference(3) meson(1) muon(1)
2024-11-28 meson.build(5)