Designing a Language

Building a language and an interpreter for it from scratch

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Progress

Note that this is a list of features that I want to implement, and not necessarily the order in which I will implement them.

What has already been implemented:

• Entire lexer implementation
• Expression parsing
• Syntax Errors
• Expression execution
• Print statements
• Variable declaration, and global scope
• Interactive REPL
• Variable assignment
• Proper runtime errors
• Synchronization and reporting multiple parse errors
• Local scope, enclosing scope, blocks and nesting
• if-else statements
• while loops
• for loops
• Logical and and or operators
• Function declarations, calls, first class functions and callbacks
• Return values
• Closures
• Compile time variable resolution and binding
• Class declarations, objects, and properties
• Class properties
• Methods
• this attribute
• Constructors
• Inheritance

Extra features

Here’s the full set of extra features, and their progress:

• Much better error messages
• Namespace concept for inbuilt libraries
• Allowing single quotes for strings
• String escapes: \n, \t, \', \", \\ and \↵
• New operators:
  • Modulo %
  • Integer division \
  • Power ^
• Lambda expressions
• New data types:
  • string: "Hello, world!"
  • int: 42
  • list: [42, 56]
  • dictionary: {42: "Forty two"}
• Indexing support: for lists, dictionaries and strings
• Comparison operators work on strings
• break and continue semantics in loops
• Exceptions, try / except blocks and raise statements
• Default values for function parameters
• *args
• Added builtin functions:
  • input
  • read and write for files
  • min, max and abs
  • map, filter and reduce that take lists and return new lists
• An import system
• Builtin Callable types
• A standard library
  • random module
  • io module string and binary reads/writes to files
  • http library to make a web server and client
  • math module