Lava is an experimental,

visual The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (the ...

object-oriented Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pro ...

, interpreter-based

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

with an associated

programming environment An integrated development environment (IDE) is a software application that provides comprehensive facilities to computer programmers for software development. An IDE normally consists of at least a source code editor, build automation tools a ...

(Lava Programming Environment or LavaPE) that uses structure editors instead of

text editor A text editor is a type of computer program that edits plain text. Such programs are sometimes known as "notepad" software (e.g. Windows Notepad). Text editors are provided with operating systems and software development packages, and can be us ...

s. Only comments, constants, and new

identifiers An identifier is a name that identifies (that is, labels the identity of) either a unique object or a unique ''class'' of objects, where the "object" or class may be an idea, physical countable object (or class thereof), or physical noncountable ...

may be entered as text. ''Declarations'' are represented in LavaPE as tree structures whose subtrees may be collapsed or expanded. The properties of the declared Lava

entities An entity is something that exists as itself, as a subject or as an object, actually or potentially, concretely or abstractly, physically or not. It need not be of material existence. In particular, abstractions and legal fictions are usually ...

can be edited through pop-up dialogs. Although ''executable code'' has a traditional text representation in LavaPE, it can be edited only as complete syntactic units, rather than character by character. If you insert a new syntactic construct, it will typically contain "placeholders" (syntactic variables) that can then be replaced by concrete constructs; the latter may in turn contain syntactic variables, etc. LavaPE provides a tool

button A button is a fastener that joins two pieces of fabric together by slipping through a loop or by sliding through a buttonhole. In modern clothing and fashion design, buttons are commonly made of plastic but also may be made of metal, wood, ...

for every type of syntactic construct, and a button is enabled only if it is syntactically correct to insert the associated construct at the selected place. Further characteristic properties of Lava and LavaPE include the following: * It provides strict syntactic separation of

interface Interface or interfacing may refer to: Academic journals * ''Interface'' (journal), by the Electrochemical Society * ''Interface, Journal of Applied Linguistics'', now merged with ''ITL International Journal of Applied Linguistics'' * '' Inte ...

(public) and

implementation Implementation is the realization of an application, or execution of a plan, idea, model, design, specification, standard, algorithm, or policy. Industry-specific definitions Computer science In computer science, an implementation is a realiza ...

(private) sections of a Lava

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...

. * It distinguishes variable "state objects" from constant "value objects"; the latter cannot be modified any longer after creation/initialization. * It supports "virtual types": type parameters of classes and packages (families of related classes). As a consequence, undermining of strong type checks by "type casts" is no longer required. * It uses

recursion Recursion (adjective: ''recursive'') occurs when a thing is defined in terms of itself or of its type. Recursion is used in a variety of disciplines ranging from linguistics to logic. The most common application of recursion is in mathematics ...

and logical quantifiers instead of traditional loop constructs. * It uses

single assignment In computer programming, an assignment statement sets and/or re-sets the value stored in the storage location(s) denoted by a variable name; in other words, it copies a value into the variable. In most imperative programming languages, the assig ...

; i.e., a value can be assigned to a variable only once within the same branch of a function. * It supports

refactoring In computer programming and software design, code refactoring is the process of restructuring existing computer code—changing the '' factoring''—without changing its external behavior. Refactoring is intended to improve the design, structure ...

extensively via the LavaPE structure editors. * It distinguishes between ''constituents'' (sub-objects) and ''object acquaintances'' (pointers to independent objects). Copying and deletion of complex objects is largely facilitated in this way. * Since release 0.9.0, LavaPE completely prevents inadvertent access to

uninitialized variable In computing, an uninitialized variable is a variable that is declared but is not set to a definite known value before it is used. It will have ''some'' value, but not a predictable one. As such, it is a programming error and a common source of bu ...

s and null objects already at programming time by complete static initialization checks. Lava is

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...

software using the

GPL The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general us ...

license (see als
Lava at the Free Software Foundation
and a
KDE-Apps.org
. It currently runs on

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...

and

Mac OS X macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac (computer), Mac computers. Within the market of ...

platforms.

References

Sources

Lava: Bausteinbasiertes Programmieren mit Struktureditoren
(German, Article in OBJEKTspektrum 1/2002)

External links

* {{Official website Class-based programming languages Experimental programming languages Free integrated development environments Linux integrated development environments Visual programming languages