Keyword Reference

Keywords are reserved words that have a special meaning in XE. They cannot be used as variable names or function names.

All Reserved Keywords

Keyword	Category	Purpose
fun	Declarations	Define a new function
fn	Declarations	Short alias for fun
function	Declarations	Alias for fun (legacy support)
struct	Declarations	Define a new composite data structure
if	Control Flow	Start a conditional block
elif	Control Flow	Add a conditional branch to an if statement
else	Control Flow	Fallback branch for an if statement
while	Loops	Start a conditional loop
for	Loops	Iterate over a list, text, or map
in	Loops	Used in the for loop syntax
repeat	Loops	Start a fixed-count loop
times	Loops	Used in the repeat loop syntax
break	Loops	Exit the current loop immediately
continue	Loops	Skip to the next iteration of the loop
pass	Control Flow	A statement that does nothing, for empty blocks
try	Errors	Run a block and handle runtime errors in it
catch	Errors	The block that runs when a try block fails
and	Logic	Logical AND operator
or	Logic	Logical OR operator
not	Logic	Logical NOT operator (also part of not in)
true	Literals	Boolean true value
false	Literals	Boolean false value
none	Literals	The absence of a value
return	Functions	Return a value from a function
global	Functions	Let a function assign to a module-level variable
lambda	Functions	Create an anonymous function: lambda x: x * 2
import	Modules	Import an entire module
from	Modules	Import specific names from a module
as	Modules	Rename an import: import helpers as h

Details by Category

Declarations

• fun, fn: Define functions. Example: fun add(a, b): or fn add(a, b):.
• function: A legacy alias for fun.
• struct: Defines user-defined composite data types with named fields. Example:

  struct Point:
      x
      y

• global: Inside a function, marks names as module-level variables so assignments update them instead of creating locals. Example: global count. See Functions and Scope.

Control Flow

• if, elif, else: Used to build decision logic. XE requires a colon : after the condition and an indented block for the body.
• pass: Does nothing; use it where a block is required but there is nothing to do.
• try, catch: Handle runtime errors. Example:

  try:
      n = convert("abc", "number")
  catch err:
      print("failed:", err)

Loops

• while: Repeats a block as long as a condition is true.
• for ... in ...: Iterates through every element in a list, every character in a text value, or every key in a map.
• repeat ... times: A high-level loop for repeating an action a specific number of times.
• break: Stops the execution of the innermost loop.
• continue: Skips the current iteration and goes to the next check/value in the loop.

Logical Operators

• and: Returns true if both operands are true.
• or: Returns true if at least one operand is true.
• not: Inverts the truthiness of a value. x not in items checks that x is absent.

Module System

• import: Loads another .xe file as a module; its members are used as module.name.
• from: Pulls specific functions, structs or variables out of a module into the current namespace.
• as: Gives an imported module or name a different local name.

Reserved Word Rule

If you try to use a keyword as a name, XE will report a syntax error during the parsing phase.

# This will fail
if = 10

Error: expected expression at line 2, column 4