cty

cty (pronounced "see-tie", emoji: 👀 👔,IPA: /si'tʰaɪ/)is a dynamic type system for applications writtenin Go that need to represent user-supplied values without losing typeinformation. The primary intended use is for implementing configurationlanguages, but other uses may be possible too.

One could think ofcty as being the reflection API for a language thatdoesn't exist, or that doesn't existyet. It provides a set of value typesand an API for working with values of that type.

Fundamentally whatcty provides is equivalent to anany with somedynamic type information attached, butcty encapsulates this to ensure thatinvariants are preserved and to provide a more convenient API.

As well as primitive types, basic collection types (lists, maps and sets) andstructural types (object, tuple), thecty type and value system has someadditional, optional features that may be useful to certain applications:

• Representation of "unknown" values, which serve as a typed placeholder fora value that has yet to be determined. This can be a useful building-blockfor a type checker. Unknown values support all of the same operations asknown values of their type, but the result will often itself be unknown.

• Representation of values whosetypes aren't even known yet. This canrepresent, for example, the result of a JSON-decoding function before theJSON data is known.

Along with the type system itself, a number of utility packages are providedthat build on the basics to help integratecty into calling applications.For example,cty values can be automatically converted to other types,converted to and from native Go data structures, or serialized as JSON.

For more details, see the following documentation:

• Concepts
• Full Description of thecty Types
• API Reference (godoc)
• Conversion betweencty types
• Conversion to and from native Go values
• JSON serialization
• cty Functions system
• Compatibility Policy for future Minor Releases: pleasereview this before usingcty in your application to avoid depending onimplementation details that may change.

License

Copyright 2017 Martin Atkins

Permission is hereby granted, free of charge, to any person obtaining a copyof this software and associated documentation files (the "Software"), to dealin the Software without restriction, including without limitation the rightsto use, copy, modify, merge, publish, distribute, sublicense, and/or sellcopies of the Software, and to permit persons to whom the Software isfurnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in allcopies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS ORIMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THEAUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHERLIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THESOFTWARE.