SPVM::Document::Language::Statements - Statements in the SPVM Language

Name Description Statements Conditional Statements Loop Statements return Statement die Statement Operator Statement Empty Statement require Statement See Also Copyright & License

Name

SPVM::Document::Language::Statements − Statements in the SPVM Language

Description

This document describes statements in the SPVM language.

Statements

A statement is a basic instruction that tells the program what to do.

Statements can be written direct under scope block.

# Scope block
{
# Statements
STATEMENT1
STATEMENT2
STATEMENT3
}

Conditional Statements

if Statement

"if" statement is a conditional statement with the following syntax.

if (CONDITION1) {
}
elsif (CONDITION2) {
}
elsif (CONDITIONn) {
}
else {
}

"elsif" statement and the "else" statement are optional.

At first, all "elsif" statements are expanded to the following code using "if" − "else" statements.

if (CONDITION1) {
}
else {
if (CONDITION2) {
}
else {
if (CONDITIONn) {
}
else {
}
}
}

"if" statement is converted to simple "if" − "else" statements, so see a simple "if" − "else" statement.

if (CONDITION) {
}
else {
}

The condition evaluation is performed on the condition CONDITION.

If the evaluated value is not 0, the program jumps to the beginning of the "if" block.

If the evaluated value is 0 and there is the "else" block, the program jumps to the beginning of the "else" block.

If the evaluated value is 0 and there is no "else" block, the program jumps to the end of the "if" block.

A "if" − "else" statement is enclosed by an invisible simple block.

{
if (CONDITION) {
}
else {
}
}

Examples:

# if statement.
my $flag = 1;
if ($flag == 1) {
say "One";
}
# if statement with elsif and else
my $flag = 2;
if ($flag == 1) {
say "One";
}
elsif ($flag == 2) {
say "Two";
}
elsif ($flag == 3) {
say "Three";
}
else {
say "Other";
}

else Statement

"else" statement is a conditional statement used in if statement.

if (CONDITION) {
}
else {
}

elsif Statement

"elsif" statement is a conditional statement used in if statement.

if (CONDITION1) {
}
elsif (CONDITION2) {
}

unless Statement

"unless" statement is a conditional statement with the following syntax.

unless (CONDITION) {
}

"unless" statement is expanded to the following code.

if (!CONDITION) {
}

Examples:

# unless statement.
my $flag = 1;
unless ($flag == 0) {
say "Not Zero";
}

switch Statement

"switch" statement is a conditional statement with the following syntax.

# switch statement
switch (CONDITION) {
case CASE1: {
# ...
}
case CASE2: {
# ...
}
case CASEn: {
# ...
}
default: {
# ...
}
}

The integer promotional conversion is performed on the condition CONDITION.

The operand of case statement CASEn must be a character literal, an integer literal and an inline−expaned class method call to get an enumeration value.

If CASEn is a character literal, the value is converted to int type at compile−time.

"case" statements and the "default" statement are optional.

If CONDITION matches CASEn, the program jumps to the beginning of the case block of CASEn.

If there are no case statements and no default statement, the program jumps to the end of the "switch" block.

If there is the "default" statement and CONDITION dose not matches CASEn, the program jumps to the beginning of the "default" block.

If there is no "default" statement and CONDITION dose not matches CASEn, the program jumps to the end of the "switch" block.

A break statement is implicitly added to the end of the statements in every "case" block.

case CASEn: {
# A break statement is added implicitly to the end of the statements
break;
}

It is allowed to jump multiple case statements into a single block.

switch (CONDITION) {
case CASE1:
case CASE2:
{
# ...
}
}

"CONDITION" in "switch statement" has own scope.

{
switch (CONDITION) {
case CASE1: {
# ...
}
case CASE2: {
# ...
}
case CASEn: {
# ...
}
default: {
# ...
}
}
}

Compilation Errors:

CONDITION must be an integer type within int. Otherwise, a compilation error occurs.

The values of the case statements must not be duplicated. Otherwise, a compilation error occurs.

Examples:

# switch statement
my $code = 2;
my $flag = 1;
switch ($code) {
case 1: {
say "1";
}
case 2: {
say "2";
}
case 3: {
if ($flag) {
break;
}
say "3";
}
case 4:
case 5:
{
say "4 or 5";
}
default: {
say "Other";
}
}
# switch statement with enumeration
class Foo {
enum {
ID1,
ID2,
ID3,
}
static method main : int () {
my $value = 1;
switch ($value) {
case Foo−>ID1: {
say "1";
}
case Foo−>ID2: {
say "2";
}
case Foo−>ID3: {
if ($flag) {
break;
}
say "3";
}
default: {
say "Other";
}
}
}
}

case Statement

"case" statement specifies a case in switch statement.

# case statement
switch (CONDITION) {
case CASEn: {
# ...
}
}

default Statement

"default" statement specifies a default case in switch statement.

# default statement
switch (CONDITION) {
default: {
# ...
}
}

break Statement

"break" statement makes the program jump to the end of switch block.

# break statement
break;

Examples:

my $code = 2;
my $flag = 1;
switch ($code) {
case 3: {
if ($flag) {
# break statement makes the program jump to the end of the switch block
break;
}
say "3";
}
default: {
say "Other";
}
}
# end of the switch block

Loop Statements

while Statement

"while" statement is a loop statement with the following syntax.

# while statement
while (CONDITION) {
}

The condition evaluation is performed on the condition CONDITION.

If the evaluated value is 0, the program jumps to the end of the "while" block. Otherwise, the program jumps to the beginning of the "while" block.

When the program reaches the end of the "while" block, it jumps to the beginning of the "while" statement.

Examples:

# while statement
my $i = 0;
while ($i < 5) {
say "$i";
$i++;
}

"while" statement is enclosed by an invisible simple block.

{
while (CONDITION) {
}
}

next Statement

"next" statement makes the program jump to the beginning of the current while statement.

# next statement
next;

Examples:

my $i = 0;
# beginning of while statement
while ($i < 5) {
if ($i == 3) {
$i++;
# next statement makes the program jump to the beginning of the current while statement.
next;
}
say "$i";
$i++;
}

last Statement

"last" statement makes the program jump to the end of the current while statement.

# last statement
last;

Examples:

while (1) {
# last statement makes the program jump to the end fo the current while statement.
last;
}
# end fo while statement

for Statement

"for" statement is a loop statement with the following syntax.

# for statement
for (INIT; CONDITION; INCREMENT) {
}

A "for" statement is expanded to the following code using a while statement.

{
INIT;
while (CONDITION) {
# ...
INCREMENT;
}
}

If CONDITION is not specified, it is set to 1.

Exampels:

# for statement
for (my $i = 0; $i < 5; $i++) {
say "$i";
}

for−each Statement

The for−each statement is a loop statement with the following syntax.

# for−each statemenet
for my VAR (@ARRAY) {
}
for my VAR (@{ARRAY}) {
}

A for−each statement is expanded to the following code using a for statement.

for (my $i = 0; $i < @{ARRAY}; $i++) {
my VAR = ARRAY−>[$i];
}

Example:

# for−each statemenet
my $array = [1, 2, 3];
for my $element (@$array) {
say "$elemenet";
}

return Statement

The return statement causes the program to return to its caller. And it set the return value.

// void
return;
// non−void
return OPERAND;

This statement causes the program to return to its caller.

If OPERAND is specified, the return vlaue is set to OPERAND.

OPERAND is an an operator.

This is because leave scope operations must not destroy OPERAND.

Compilation Errors:

If the return type of the current method is the void type, OPERAND must not exist. Otherwise, a compilation error occurs.

If the return type of the current method is the non−void type, OPERAND must exist. Otherwise, a compilation error occurs.

The type of OPERAND must satisfy assignment requirement to the return type of the current method. Otherwise, a compilation error occurs.

die Statement

"die" statement throws an exception.

# die statement
die
die OPERAND_MESSAGE
# die statement with an error class
die ERROR_CLASS
die ERROR_CLASS OPERAND_MESSAGE
# die statement with the basic type ID of an error class
die OPERAND_ERROR_ID, OPERAND_MESSAGE
die $@

OPERAND_MESSAGE is a string of string type for an error message. If the exception thrown by the "die" statement is catched, exception variable $@ is set to OPERAND_MESSAGE with stack traces added.

If the exception is not catched, the program prints it to SPVM's standard error, and finishes the program with an error ID.

The following is an example of stack traces of an exception message.

Error
TestCase::Minimal−>sum2 at SPVM/TestCase/Minimal.spvm line 1640
TestCase−>main at SPVM/TestCase.spvm line 1198

If OPERAND_MESSAGE is not given or "undef", OPERAND_MESSAGE is set to "Error".

ERROR_CLASS is a class name, normally of Error class, or its child class. If the exception thrown by the "die" statement is catched, eval_error_id is set to the basic type ID of ERROR_CLASS.

The integer promotional conversion is performed on OPERAND_ERROR_ID.

OPERAND_ERROR_ID is an integer value within int type. If it is given and the exception thrown by the "die" statement is catched, eval_error_id is set to OPERAND_ERROR_ID.

See also Exception Handling for exception handling using the "die" statement.

If the operand is $@ and OPERAND_ERROR_ID is not specified, a special interpretation is applied.

die $@

is replaced with

die eval_error_id, $@

Operator Statement

The operator statement operates an operator.

# operator statemenet
OPERATOR;

Examples:

1;
$var;
1 + 2;
&foo();
my $num = 1 + 2;

Empty Statement

The empty statement operates nothing.

# empty statemenet
;

require Statement

"require" statement loads a class only if it is found.

if (require BASIC_TYPE) {
}
if (require BASIC_TYPE) {
}
else {
}

This statement searches for the type BASIC_TYPE in class search directories from the beginning, and if found, it loads BASIC_TYPE at compilation time.

If BASIC_TYPE is found, the "if" block is converted to a simple block and the "else" block(if it eixsts) is removed at compilation time.

If BASIC_TYPE is not found, a compilation error does not occur.

If BASIC_TYPE is not found, the "else" block (if it eixstgs) is converted to a simple block and the "if" block is removed at compilation time.

Examples:

my $foo : object;
if (require MyClass) {
$foo = new MyClass;
}
else {
warn "Warning: Can't load MyClass";
}

Copyright & License

MIT License

Updated 2026-06-01 - jenkler.se | uex.se

	•		SPVM::Document::Language::Class
	•		SPVM::Document::Language::Operators
	•		SPVM::Document::Language
	•		SPVM::Document