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Heron Compared to TypeScript / JavaScript

Heron most closely resembles a subset of the JavaScript language. It has a type system that is more restricted than TypeScript, but the type-inference system is more aggressive. For example Heron function parameter types are inferred based on usage in the function defintion, as opposed to resolving to any.

The biggest standout difference is that Heron has no concept of classes or prototypes.

Heron is an unordered list of various differences Heron has with TypeScript/JavaScript:

  • only primitive types, generic types (including array and function), and type variables
  • no object literals
  • no this keyword
  • functions can be called using dot notation on the first argument
  • functions can be ovoverloaded (two functions can have the same name if the inferred types are different)
  • operators can be overloaded
  • operators can be passed as functions
  • var statements are equivalent to let statements in TypeScript/JavaScript
  • no const statements
  • module level variables cannot be modified
  • variable types are inferred
  • parameter and return types of functions are inferred
  • variables have to always be initialized
  • variable binding expression allows variable declarations to be used as expressions
  • arrays are immutable
  • modifying arrays can only be done with ArrayBuilder
  • each ArrayBuilder modification creates a new array
  • only supports a for..in loop form which is the same as for..of loop in JavaScript
  • a built-in range operator from..to generates an array of contiguous values (exclusive upper bound)
  • arrays do not necessarily allocate memory, e.g. 0..100000000, has O(1) memory consumption
  • module names are URN's with the version number encoded in it
  • all files specify the version of the language
  • all definitions must be in a module
  • variables cannot be reassigned to objects of a different type
  • no async or await support
  • no operators spread support
  • no class or interface definitions
  • anonymous functions use a fat arrow syntax
  • Separation betwen integers (Int) and floating point numbers (Float)
  • Support for two, three, and four dimensional numerical types like in GLSL (Float2, Float3, Float4).
  • Semicolons are required as statement terminators.
  • No statement labels
  • No comma operator
  • No switch statement