Cmel

Cmel (see-mel) is short for Caramel, the name of my cat. It's my implementation of Lox from Crafting Interpreters by Robert Nystrom.

Features

Here are the features which separate Cmel from Lox.

• Support for 2^24 constant values in a script
• Local const values
• Has a break statement to exit from loops early
• Built-ins
• Primitive methods (e.g. "string".length())
• Lists
• Modulo operator

Primitive Types

• Nil
• Boolean
• String
  • length() returns the number of characters in the string
  • split(delimiter) returns a list of elements in the given string as separated by the delimiter
• Number
  • add(Number) returns the number plus the passed number
• List
  • add(value) mutates the list by adding the given value and returns the same list
  • remove(index) mutates the list by removing the value at the given index and returns the same list
  • length() returns the length of the list

Built-in Functions

• input() gets and returns a value from stdin
• clock() returns the current time since the program started in seconds
• readFile(path) returns the content of the given path as a String
• number(val) returns a number representation of the given value. Only numbers, booleans and strings may be passed

Usage

Compile the project using

./build.sh

Then, you can either run cmel as a REPL

./cmel

or execute a file by passing it the path

./cmel <filepath>

Testing

To test the code, first build the executable using the build script, then navigate to the test folder and run

node --test

Todo

Language Features

• Widen const to work for global variables
• Arrays/Lists
• File Reading
• Postfix Operators (e.g. ++ and --)
• Ternary Operator
• Modulo Operator
• String Escape Characters
• String interpolation
• Implicit convert to string on all types for concatenation
• Try/Catch
• Anonymous Functions
• Modules
• User facing Hash Tables (Including non-string keys)
• Continue Statement
• Break Statement
• Switch Statement
• Typeof operator
• toString method on instances

Tooling

• Syntax Highlighter
• Language Server
• Test Runner

Misc

• In chapter 18 it's mentioned that a <= b should not be the same as !(a > b) but in cmel it is. Fix by introducing dedicated instructions for <=, >= and maybe != while you're at it