Project Property

A project property is a compile time constant which is given through Veryl.toml instead of source code. It is useful to configure a project from the outside of the source code. For example, a library can be built with a different data width for each project which depends on it.

Definition

Project properties are defined in the [properties] section of Veryl.toml. The value of a property is an integer or a boolean.

[project]
name    = "veryl_sample"
version = "0.1.0"

[properties]
DATA_WIDTH   = 32
ENABLE_DEBUG = false

See Project Configuration for detailed information.

Reference

Defined properties can be referenced through the $prop namespace. An integer property has i64 type, and a boolean property has bbool type.

package sample_pkg {
    const DATA_WIDTH  : i64   = $prop::DATA_WIDTH;
    const ENABLE_DEBUG: bbool = $prop::ENABLE_DEBUG;
}

$prop always refers to the properties of the project which the source code belongs to. So the properties of a dependency can’t be referenced from the project which depends on it.

A project property is a compile time constant, so it can be used wherever a constant expression can be used. The value is resolved at compile time, and the resolved value appears in the generated code.

module ModuleA {
    var a: logic<$prop::DATA_WIDTH>;

    if $prop::ENABLE_DEBUG :g_debug {
        // debug logic
    }
}

Configuration by the depending project

The value of a project property can be overridden through the properties field of the [dependencies] section by the project which depends on it.

[dependencies]
veryl_sample = {github = "veryl-lang/veryl_sample", version = "0.1.0", properties = {DATA_WIDTH = 8}}

In the above example, $prop::DATA_WIDTH in veryl_sample becomes 8. The properties which are not specified here keep the default values defined in Veryl.toml of the dependency, so $prop::ENABLE_DEBUG keeps false.

See Dependencies for detailed information.