NEPLg1

Workspace for the Neknaj Expression Prefix Language (NEPL) toolchain. The repository currently contains a core crate that lexes, parses, and validates a small arithmetic-focused subset of NEPL, plus a command-line interface for compiling sources to WebAssembly or LLVM IR.

Crates

• nepl-core: Loads the .nepl standard library files from ./stdlib, parses prefix expressions (add, sub, mul, div, mod, pow, neg, comparisons, bitwise ops, logic ops), validates them, and emits executable WebAssembly modules or LLVM IR that returns the computed value.
• nepl-cli: Provides a Clap-based CLI for compiling sources, writing output artifacts, and executing WebAssembly output through wasmi.

Usage

Compile a source file to WebAssembly and run it:

cargo run -p nepl-cli -- --input examples/io_pipeline.nepl --output target/io_pipeline.wasm --run

Emit LLVM IR instead:

cargo run -p nepl-cli -- --input examples/io_pipeline.nepl --output target/io_pipeline.ll --emit llvm

The CLI accepts input from stdin when --input is omitted.

Examples

Practical examples live under examples/:

• io_pipeline.nepl threads together arithmetic, vector access, string utilities, and standard I/O built-ins. It prints the length of a concatenated string and a computed value based on a host-provided random number before returning their sum.

Supported expression forms

The current implementation supports prefix arithmetic expressions built from the operators add, sub, mul, div, mod, pow, neg, comparisons (lt, le, eq, ne, gt, ge), bitwise operators, and boolean operators (and, or, not, xor), using integer literals. Parentheses can be used to group expressions. Imports for target-specific built-ins are generated when you reference them in source code, and nepl-cli --run links default host behavior through wasmi 0.51:

• wasm_pagesize imports env.wasm_pagesize and returns the host-provided page size (default: 65,536 bytes).
• wasi_random imports wasi_snapshot_preview1.wasi_random and returns a deterministic host number (default: 4).
• wasi_print <value> imports wasi_snapshot_preview1.wasi_print to emit the value and return it for further chaining. The default host implementation prints to stdout.

The pipe operator > is available as a convenience for threading the previous result into the next function call. For example, 1 > neg > add 2 desugars to add (neg 1) 2.

Web playground

An experimental browser playground lives under web/. To embed the external editor used for NEPL snippets, clone the editor repository before serving the page:

scripts/fetch_editorsample.sh

The script clones https://github.com/bem130/editorsample into web/vendor/editorsample. Set EDITOR_SAMPLE_REPO, EDITOR_SAMPLE_REF, or EDITOR_SAMPLE_DEST to override the repository, ref, or destination root for testing or offline mirroring. After cloning, serve web/index.html (for example with trunk serve or any static file server) to load the editor iframe and the playground scaffolding.

To keep long-running or infinite programs from blocking the browser, the nepl-web-playground crate exposes a fuel-driven stepper around wasmi with fuel metering enabled. Build it for wasm32-unknown-unknown and wrap its API from JavaScript to slice execution into short ticks: add fuel, call run_slice until it returns finished, or stop early by clearing any pending resumable call.

Standard library layout

Place .nepl files under ./stdlib. The core crate loads every .nepl file recursively and records the relative path and contents in the CompilationArtifact so downstream tooling can embed or inspect the bundled library. The CLI uses this bundled path by default, and you can point it to an alternate root with --stdlib /path/to/stdlib when testing different library layouts. Platform shims live under stdlib/platform and wrap the WASM/WASI built-ins exposed by the compiler.

Testing

Run host tests for all crates:

cargo test --workspace

Validate the core crate against the wasm32-unknown-unknown target:

cargo test --target wasm32-unknown-unknown --no-run -p nepl-core