NickelEval.jl

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NickelEval.jl ​

Julia bindings for the Nickel configuration language, using the official Nickel C API.

Evaluate Nickel code directly from Julia and get back native Julia types — no CLI, no intermediate files, no serialization overhead.

Features ​

  • Direct evaluation of Nickel expressions and files via the C API

  • Native type mapping — records become Dict, arrays become Vector, enums become NickelEnum

  • Typed evaluation — request results as Dict{String,Int}, Vector{Float64}, NamedTuple, etc.

  • Export to JSON, TOML, YAML — serialize Nickel configurations to standard formats

  • File evaluation with imports — evaluate .ncl files that reference other Nickel files

Documentation ​

Installation ​

From the LouLouLibs Registry ​

julia
using Pkg
Pkg.Registry.add(url="https://github.com/LouLouLibs/loulouJL")
Pkg.add("NickelEval")

From GitHub ​

julia
using Pkg
Pkg.add(url="https://github.com/LouLouLibs/NickelEval.jl")

Pre-built native libraries are provided for macOS (Apple Silicon) and Linux (x86_64). On supported platforms, the library downloads automatically when first needed.

Building from Source ​

If the pre-built binary doesn't work on your system — or if no binary is available for your platform — you can build the Nickel C API library from source. This requires Rust.

julia
using NickelEval
build_ffi()

This clones the Nickel repository, compiles the C API library with cargo, and installs it into the package's deps/ directory. The FFI is re-initialized automatically — no Julia restart needed.

You can also trigger the build during package installation:

julia
ENV["NICKELEVAL_BUILD_FFI"] = "true"
using Pkg
Pkg.build("NickelEval")

Older Linux Systems (glibc Compatibility) ​

The pre-built Linux binary is compiled against a relatively recent version of glibc. On older distributions — CentOS 7, older Ubuntu LTS, or many HPC clusters — you may see an error like:

/lib64/libm.so.6: version `GLIBC_2.29' not found

The fix is to build from source:

julia
using NickelEval
build_ffi()

This compiles Nickel against your system's glibc, producing a compatible binary. The only requirement is a working Rust toolchain (cargo), which can be installed without root access via rustup:

bash
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

After installing Rust, restart your Julia session and run build_ffi().