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Supported Types for Variables and Parameters

The SARL programming language is statically-typed, which means that all variables and parameters must first be declared before they can be used. This involves stating the variable’s type and name, as you’ve already seen:

var gear : int = 1

Doing so tells your program that a field named gear exists, holds numerical data, and has an initial value of 1. A variable’s data type determines the values it may contain, plus the operations that may be performed on it. In addition to int, the SARL programming language supports other data types:

##1. Primitive Types

A primitive type is predefined by the language and is named by a reserved keyword. Primitive values do not share state with other primitive values. The eight primitive data types supported by the SARL programming language are:

Type Object Equivalent (Wrapper) Definition
byte java.lang.Byte The byte data type is an 8-bit signed two’s complement integer. It has a minimum value of -128 and a maximum value of 127 (inclusive). The byte data type can be useful for saving memory in large arrays, where the memory savings actually matters. They can also be used in place of int where their limits help to clarify your code; the fact that a variable’s range is limited can serve as a form of documentation.
short java.lang.Short The short data type is a 16-bit signed two’s complement integer. It has a minimum value of -32,768 and a maximum value of 32,767 (inclusive). As with byte, the same guidelines apply: you can use a short to save memory in large arrays, in situations where the memory savings actually matters.
int java.lang.Integer By default, the int data type is a 32-bit signed two’s complement integer, which has a minimum value of -2^31 and a maximum value of 2^(31)-1. In SARL, you can use the int data type to represent an unsigned 32-bit integer, which has a minimum value of 0 and a maximum value of 2^(32)-1. Use the Integer class to use int data type as an unsigned integer. Static methods like compareUnsigned, divideUnsigned etc have been added to the Integer class to support the arithmetic operations for unsigned integers.
long java.lang.Long The long data type is a 64-bit two’s complement integer. The signed long has a minimum value of -2^63 and a maximum value of 2^(63)-1. In SARL, you can use the long data type to represent an unsigned 64-bit long, which has a minimum value of 0 and a maximum value of 2^(64)-1. Use this data type when you need a range of values wider than those provided by int. The Long class also contains methods like compareUnsigned, divideUnsigned etc to support arithmetic operations for unsigned long.
float java.lang.Float The float data type is a single-precision 32-bit IEEE 754 floating point. Its range of values is beyond the scope of this discussion, but is specified in the Floating-Point Types, Formats, and Values section of the SARL Language Specification. As with the recommendations for byte and short, use a float (instead of double) if you need to save memory in large arrays of floating point numbers. This data type should never be used for precise values, such as currency. For that, you will need to use the java.math.BigDecimal class Numbers and Strings covers BigDecimal and other useful classes provided by the SARL platform.
double java.lang.Double The double data type is a double-precision 64-bit IEEE 754 floating point. Its range of values is beyond the scope of this discussion, but is specified in the Floating-Point Types, Formats, and Values section of the SARL Language Specification. For decimal values, this data type is generally the default choice. As mentioned above, this data type should never be used for precise values, such as currency.
boolean java.lang.Boolean The boolean data type has only two possible values: true and false. Use this data type for simple flags that track true/false conditions. This data type represents one bit of information, but its “size” isn’t something that’s precisely defined. 
char java.lang.Character The char data type is a single 16-bit Unicode character. It has a minimum value of \u0000 (or 0) and a maximum value of \uffff (or 65,535 inclusive).

##2. String of Characters

In addition to the eight primitive data types listed above, the SARL programming language also provides special support for character strings via the java.lang.String class. Enclosing your character string within (double or simple) quotes will automatically create a new String object; for example, var s : String = "this is a string".

String objects are immutable, which means that once created, their values cannot be changed. The String class is not technically a primitive data type, but considering the special support given to it by the language, you’ll probably tend to think of it as such.

##3. Default Values of Primitive Types

It’s not always necessary to assign a value when a field is declared. Fields that are declared but not initialized will be set to a reasonable default by the compiler. Generally speaking, this default will be zero or null, depending on the data type. Relying on such default values, however, is generally considered bad programming style.

The following chart summarizes the default values for the above data types.

Data Type Default Value
byte 0
int 0
long 0
float 0
double 0
char 0
boolean false
String or any object null

##4. Acknowledgements

This documentation is inspired by the documentations from the Xtext and Xtend projects.

##5. Legal Notice

Copyright © 2014-2019 the original authors or authors.

Licensed under the Apache License, Version 2.0; you may not use this file except in compliance with the License. You may obtain a copy of the License.

You are free to reproduce the content of this page on copyleft websites such as Wikipedia.

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