Nexus

Nexus is a small interpreted scripting language implemented in C++.

This README tracks project progress and documents what currently works.

Current Status

✅ Done

• CLI entrypoint that reads source from a file path or stdin.
• Lexer with:
  • identifiers, numbers, strings
  • operators: + - * / > < = ==
  • punctuation: () { } ;
  • keywords: let const out if else repeat times
  • comments: // line and /* block */
  • line/column diagnostics with source name
• Parser + AST with:
  • declarations: let, const
  • output statement: out(...)
  • control flow: if / else if / else
  • loops: repeat <ident> <expr> times { ... }
  • expression precedence: equality, comparison, add/sub, mul/div, grouping
• Runtime with:
  • integer arithmetic and comparisons
  • variable declarations and reassignment (x = ...;)
  • block-based lexical scoping for { ... }, if/else, and repeat bodies
  • nested loop/conditional scope isolation (inner variables do not overwrite outer scope bindings)
  • runtime diagnostics (with caret and location)

🚧 In Progress / Not Implemented Yet

• variable environment + const tracking
• runtime diagnostics (with caret and location)

🚧 In Progress / Not Implemented Yet

• Assignment to existing variables (e.g. x = x + 1;)
• Functions and function calls
• Modules/imports
• Rich types (arrays, maps/objects, booleans as first-class type)
• Standard library (fs, http, json, process, etc.)
• Bytecode VM / JIT (performance-focused execution backend)
• Automated tests in CTest

🎯 Next Milestones

1. Add functions + call stack.
2. Add core stdlib (IO, JSON, HTTP, process).
3. Move from AST-walk execution toward bytecode for speed.
4. Add test suite + benchmarks.
5. Add assignment statements and scoped blocks.
6. Add functions + call stack.
7. Add core stdlib (IO, JSON, HTTP, process).
8. Move from AST-walk execution toward bytecode for speed.
9. Add test suite + benchmarks.

---

Build

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build --config Release -j"$(nproc)"

Run from file:

./build/nexus examples.nxt
./build/nexus examples.nx

Or pipe from stdin:

echo 'out("hello");' | ./build/nexus

Source files are required to use the .nxt extension when passed as a file argument.

---

Language Examples

1) Variables and output

```nx
let x = 10;
const y = 3;
out(x + y);

Expected output:

13

2) Looping

```nx
repeat i 5 times {
  out(i);
}

Expected output:

0
1
2
3
4

3) Reassignment and scoped blocks

let x = 1;
{
  let x = 10;
  x = x + 5;
  out(x);
}
out(x);

Expected output:

15
1

4) Nested loop scope isolation

let i = 99;
repeat i 2 times {
  out(i);
  {
    let i = 42;
    out(i);
  }
}
out(i);

Expected output:

0
42
1
42
99

5) Conditionals

## 3) Conditionals

```nx
let n = 7;
if n > 10 {
  out("big");
} else if n == 7 {
  out("lucky");
} else {
  out("small");
}

Expected output:

lucky

6) Comments and grouping

## 4) Comments and grouping

```nx
// line comment
/* block
   comment */
out((2 + 3) * 4);

Expected output:

20

---

Docker

Build image:

docker build -t nexus:local .

Run with stdin:

echo 'out("from container");' | docker run --rm -i nexus:local

---

CI/CD Notes

The Docker publish workflow builds the project via CMake inside the image build stage. If C++ compilation fails, the Docker build step will fail as expected.