cue: return an ast.Expr instead of Instance

Fixes cuelang/cue#21.

Change-Id: I214a7bf96db69d02deedc6db06c3b5945298d9dc
5 files changed
tree: fc231fbf7da131f66783582f8f7d86bbed0237e3
  1. cmd/
  2. cue/
  3. doc/
  4. internal/
  5. pkg/
  8. go.mod
  9. go.sum

The CUE Data Constraint Language

Configure, Unify, Execute

CUE is an open source data constraint language which aims to simplify tasks involving defining and using data. It can be used for data templating, data validation, and even defining scrips operating on data.

CUE is a constraint-based language. Constraints act both as data templates and detailed type definitions. Constraints provide a powerful yet simple alternative to inheritance, a common source of complexity with existing configuration languages. Constraints also provide an expressive way to define the possible values of data types, which in turn can be used for data validation in various applications.

The CUE tooling also provides integrated declarative scripting aimed at simplifying putting configurations to good use while giving static analysis tools maximum domain knowledge.

Some highlights:

  • JSON superset: get started quickly
  • convert existing YAML and JSON
  • declarative scripting
  • automatically simplify configurations
  • formatter
  • arbitrary-precision arithmetic
  • rich APIs designed for automated tooling
  • a formalism conducive to automated reasoning
  • generate CUE templates from source code
  • generate source code from CUE configurations (TODO)

Download and Install

Install From Source

If you already have Go installed, the short version is:

go get -u

This will install the cue command line tool.

For more details see Installing CUE.

Learning CUE

The fastest way to learn the basics is to follow the tutorial on basic language constructs.

A more elaborate tutorial demonstrating of how to convert and restructure an existing set of Kubernetes configurations is available in written form.



Our canonical Git repository is located at

To contribute, please read the Contribution Guide.

To report issues or make a feature request, use the issue tracker.

Note that we do not accept pull requests and that we use the issue tracker for bug reports and proposals only.

Unless otherwise noted, the CUE source files are distributed under the Apache 2.0 license found in the LICENSE file.

This is not an officially supported Google product.