Statements

All functions are made up of a list of statements enclosed with left and right braces, which in and of itself is a statement called a compound statement, or block.

Statement

• CompoundStatement
• ConditionalStatement
• FlowStatement
• ExpressionStatement
• LocalVariableStatement
• LoopStatement
• MultiAssignmentStatement
• NullStatement
• StaticArrayDefinition
• SwitchStatement

Compound Statements

Note that the statement list is zero or more, so an empty compound statement {} is entirely valid.

CompoundStatement

{ Statement* }

Expression Statements

An expression statement is the single most common type of statement in just about any programming language. In ZScript, exactly like C and C++, an expression statement is simply formed with any expression followed by a semicolon. Function calls and variable assignments are expressions, for instance, so it is quite clear why they are common.

ExpressionStatement

Expression ;

Conditional Statements

A conditional statement will, conditionally, choose a statement (or none) to execute. They work the same as in C, C++, and ACS.

ConditionalStatement

if ( Expression ) Statement (else Statement)?

Switch Statements

A switch statement takes an expression of integer or name type and selects a labeled statement to run. They work the same as in C, C++, and ACS.

SwitchStatement

switch ( Expression ) Statement

Loop Statements

ZScript has five loop statements: for, while, until, do while and do until. for, while and do while work the same as in C, C++ and ACS, and until and do until do the inverse of while and do while.

LoopStatement

• ForLoopStatement
• WhileLoopStatement
• DoWhileLoopStatement

For Loop Statements

The for loop takes a limited statement and two optional expressions: The statement for when the loop begins (which is scoped to the loop,) one expression for checking if the loop should break, and one which is executed every time the loop iterates.

ForLoopStatement

for ( ForLoopInitializer? ; ForLoopUpdate? ; Expression? ) Statement

ForLoopInitializer

• LocalVariableStatement
• ForLoopUpdate

ForLoopUpdate

Expression (, Expression)*

While Loop Statements

The while loop simply takes one expression for checking if the loop should break, equivalent to for(; x;).

The until loop is equivalent to while(!x).

WhileLoopStatement

• while ( Expression ) Statement
• until ( Expression ) Statement

Do While Loop Statements

do while and do until will only check the expression after the first iteration is complete. Unlike C, you don't need a semicolon after one.

DoWhileLoopStatement

• do Statement while ( Expression )
• do Statement until ( Expression )

Flow Statements

As in C, there are three control flow statements that manipulate where the program will execute statements next, which are available contextually. They are continue, break and return.

FlowStatement

• ContinueFlowStatement
• BreakFlowStatement
• ReturnFlowStatement

Continue Flow Statements

continue is available in loop statements and will continue to the next iteration immediately.

ContinueFlowStatement

continue ;

Break Flow Statements

break is available in loop statements and switch statements, and will break out of the containing statement early.

BreakFlowStatement

break ;

Return Flow Statements

return is available in functions. If the function does not return any values, it may have no expressions, and will simply exit the function early. If the function does return values, it takes a comma-separated list for each expression returned.

ReturnFlowStatement

return (Expression (, Expression)*)? ;

Local Variable Statements

Local variable statements define one or more variables in the current scope.

LocalVariableStatement

Type LocalVariableInitializer (, LocalVariableInitializer)* ;

LocalVariableInitializer

• VariableName
• VariableName = Expression

Multi-Assignment Statements

Expressions or functions that return multiple values can be assigned into multiple variables.

MultiAssignmentStatement

[ Expression (, Expression)* ] = Expression ;

Null Statements

A null statement does nothing. It is similar to an empty compound statement.

NullStatement

;

Examples

Expression Statements

// Some basic expressions.
MyCoolFunction(5, 4);
m_MyCoolMember = 500;

// Does nothing, of course, but valid.
5 * 5;

Conditional Statements

// Simple conditional.
if(a)
	B();

// Simple conditional, with else statement and a block.
if(a)
{
	B();
	c = d;
}
else
	e = f;

Switch Statements

// A switch demonstrating fall-through and default cases.
switch(a)
{
case 500:
	Console.PrintF("a is 500");
	break;
case 501:
	Console.PrintF("a is 501");
	// Falls through to the next case.
case 502:
	Console.PrintF("a is 501 or 502");
	break;
default:
	Console.PrintF("not sure what a is!");
	// "break" is implied here.
}

Flow Statements

// Use of "continue."
for(int i = 0; i < 50; i++)
{
	// Don't do anything when "i" is 25.
	if(i == 25)
		continue;

	DoThing(i);
}

// Use of "break."
for(int i = 0; i < 50; i++)
{
	// "break" when "i" is 25.
	if(i == 25)
		break;

	DoThing(i);
}

// Use of `return` in various contexts.
void ReturnsNothing()
{
	// Exit early if "m_Thing" isn't 50.
	if(m_Thing != 50)
		return;

	DoThing(m_Thing);
}

int ReturnsInt()
{
	// "m_Thing" is 50, so return 50.
	if(m_Thing == 50)
		return 50;

	// Must have a return, eventually.
	return 0;
}

int, int ReturnsTwoInts()
{
	// Returns 1 and 2.
	return 1, 2;
}

Multi-Assignment Statements

// Getting the actor out of "A_SpawnItemEx."
Actor mo; bool spawned; [spawned, mo] = A_SpawnItemEx("MyCoolActor");