Language Reference

For a complete list of reserved words, see the Keyword Reference.

Data types

Type	Example	Notes
number	42, 3.14	Numeric values
text	"hello"	String values
boolean	true, false	Condition values
list	[1, 2, 3]	Ordered values with zero-based indexing

XE uses an inferred type system with a Typed IR. The compiler maps variables to native Rust types for performance, falling back to a dynamic XeValue only when types are mixed or unknown.

Invalid operations now fail with explicit runtime errors instead of silently producing fallback values.

Operators

Arithmetic

• +
• -
• *
• /
• %

Comparison

• ==
• !=
• <
• >
• <=
• >=

Logic

• and
• or
• not

Built-in functions

Function	Purpose	Example
print(...)	Print one or more values	print("hi")
input(prompt)	Read text from the user	name = input("Name? ")
length(value)	Return length of text or list	length([1, 2, 3])
type(value)	Return the XE type name as text	type(42)
convert(value, target)	Convert between supported types	convert("42", "number")

Valid convert targets:

• "number"
• "text"
• "boolean"

Control flow

• if
• elif
• else
• repeat N times
• while
• for name in iterable
• break
• continue

for loops currently iterate over:

• lists
• text values, one character at a time

Function syntax

fun name(arg1, arg2):
    return arg1 + arg2

Functions can access:

• parameters
• variables created inside the function
• built-in functions
• other user-defined functions
• imported user-defined functions
• global module-level variables

They do not yet support nested closures (capturing local variables from an outer function).

Modules and imports

XE modules are other .xe files.

from math_utils import double
print(double(21))

Available forms:

• import helpers
• from helpers import square, cube

Current rules:

• imports resolve relative to the importing file
• import module_name brings that module's top-level functions into scope
• from module_name import name imports selected top-level functions
• only top-level functions are importable today
• imports must appear before executable top-level statements
• imported module top-level code runs once before the entry module's top-level code

Example project shape:

• main.xe
• helpers.xe

Notes on formatting

• XE uses indentation-based blocks
• spaces are the expected style for indentation
• there are no braces for if, elif, else, repeat, while, for, or fun blocks

Assignment semantics

• name = value creates a variable if that name does not exist in any enclosing scope
• otherwise, it reassigns the nearest existing variable instead of creating a shadow copy
• names first created inside a block stay local to that block

Error behavior

• compiler errors include line/column information, the source line, and a caret marker
• invalid runtime operations stop the program with a Runtime error: ... message