Expressif 2.5.2

Expressif

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Expressif is a language for defining data transformations, validations, computations, and aggregations as expressions. It was created for nbi.io and has grown into a portable language and function library for working with scalar and structured data.

Expressions are designed to be:

• Readable: values flow from left to right through explicit transformations.
• Predictable: operations favor safe results, such as #null, over avoidable exceptions.
• Composable: small expressions combine into pipelines for filtering, mapping, and aggregation.
• Portable: the language is designed to retain its meaning across runtime ecosystems.

Read the documentation · Learn the language · Browse the reference · View releases

The language

An Expressif expression receives a value, applies a transformation, and produces a result. The pipe operator (|) passes the output of each operation to the next one.

"  Alice  " | trim | upper

The same model scales to structured data and collections:

@orders
| filter(.active)
| map(.amount)
| sum

Predicates are expressions that produce Boolean values. Predicate combinators apply multiple conditions to the same input:

greater-than(0) |AND less-than(100)

See the language guide for expressions, values and types, references, structured values, and predicates.

Use Expressif

.NET SDK

The Expressif NuGet package targets .NET 8, .NET 9, and .NET 10.

dotnet add package Expressif

Create an expression and evaluate an input value:

using Expressif;

var expression = Expression.Create("trim | upper");
var result = expression.Evaluate("  Alice  ");

The .NET SDK also provides APIs for predications, typed builders, runtime context, and serialization. Continue with the .NET SDK guide.

Command-line interface

Install the CLI as a .NET global tool:

dotnet tool install --global Expressif-cli
expressif version

The CLI can evaluate expressions, process input data, validate source text, inspect parsing and binding, and display function help.

expressif evaluate '"  Alice  " | trim | upper'

Windows installers and portable archives for Windows and Linux are also available from GitHub Releases. See the CLI guide for commands, input sources, diagnostics, and automation guidance.

Documentation

The documentation site is the authoritative guide and reference:

• Getting started
• Language guide
• Function reference
• Predicate reference
• Accumulator reference
• .NET SDK
• Command-line interface
• Tooling and editor support

Function, predicate, and accumulator details live in these references rather than being duplicated in this README.

Tooling

Expressif provides syntax highlighting for Visual Studio Code, TextMate consumers, Notepad++, and Rouge. Language-aware diagnostics and completion are available through the Expressif Language Server.

Download the editor assets that match your Expressif version from GitHub Releases, then follow the tooling documentation for installation and capabilities.

Contributing

Issues, feature ideas, and pull requests are welcome. Read CONTRIBUTING.md before making a change, use GitHub Discussions for broader questions, or report a problem through GitHub Issues.

License

Expressif is licensed under the Apache License 2.0.