Gosu (programming language)

Gosu is often described as a Java variant that introduces practical improvements while maintaining compatibility and interoperability with Java. The language originated in 2002 at Guidewire Software, where it was first named GScript, a scripting language designed for use in Guidewire applications.^[3][4] As GScript evolved from a simple scripting tool into a general-purpose programming language, it was renamed Gosu by its lead developer, Scott McKinney.

Originally created as a glue language to allow Guidewire customers to define business rules, Gosu quickly found broader use within the company’s products, supporting areas such as user interface bindings, templating, and document management. Over time, Gosu became the main implementation language across Guidewire’s application suite, surpassing Java in overall use.

Guidewire released Gosu 0.7 beta to the public in November 2010, followed by 0.8 beta in December 2010 and 0.8.6 beta in mid-2011. These releases introduced several enhancements, including new typeloaders that allowed Gosu to dynamically represent external data formats such as JavaScript Object Notation (JSON) and Extensible Markup Language (XML) as native Gosu types.

Guidewire continues to use and support Gosu extensively within its InsuranceSuite applications. While active development of new Gosu language features has been paused, the company continues to expand InsuranceSuite through Representational State Transfer (REST) application programming interfaces (APIs) and integration frameworks accessible from Gosu and Java.

Gosu language creator and development lead, Scott McKinney, emphasizes pragmatism, found in readability and discoverability, as the overriding principle that guides the language's design.^[5] For instance, Gosu's rich static type system is a necessary ingredient toward best of breed tooling via static program analysis, rich parser feedback, code completion, deterministic refactoring, use analysis, navigation, and the like.

Gosu follows a syntax resembling a combination of other languages. For instance, declarations are similar to Pascal with name-first grammar. Gosu classes can have functions, fields, properties, and inner classes as members. Nominal inheritance and composition via delegation are built into the type system and structural typing similar to the Go language.

Gosu supports several file types:

• Class (.gs files)
• Program (.gsp files)
• Enhancement (*.gsx files)
• Template (*.gst files)

In addition to standard class types Gosu supports enums, interfaces, structures, and annotations.

Program files facilitate Gosu as a scripting language. For example, Gosu's "Hello, World!" program is a simple one-line string:

print("Hello, World!")

Gosu classes are also executable a la Java:

class Main {
  static function main(args: String[]) {
    print("Hello, World!")
  }
}

enhancement MyStringEnhancement : String {
  function print() {
    print(this)
  }
}

"Echo".print()

var list = {1, 2, 3}
var result = list.where(\ elem -> elem >= 2)
print(result)

This general-purpose programming language is used mainly in Guidewire Software's commercial products.