Leo RFC 011: Scalar Type Accesses And Methods

Authors

Max Bruce
Collin Chin
Alessandro Coglio
Eric McCarthy
Jon Pavlik
Damir Shamanaev
Damon Sicore
Howard Wu

Status

DRAFT

Summary

This RFC proposes two things:

The scalar types in Leo (integers, fields, etc.) can have static methods.
The scalar types in Leo (integers, fields, etc.) can have static constants.
Those values that have a scalar type can have methods directly on them.

Motivation

This approach allows for a clean interface to provide built-in methods or static members for these basic types.

Design

Semantics

Firstly we would have to modify both the ABNF and parsing of Leo to allow static method calls onto a scalar type.

The ABNF would look as follows:

; This is an existing old rule
scalar-type =  boolean-type / arithmetic-type / address-type / character-type

; This is an existing old rule
circuit-type = identifier / self-type

; Add this rule.
named-type = circuit-type / scalar-type ; new rule

; Modify this rule:
postfix-expression = primary-expression
                   / postfix-expression "." natural
                   / postfix-expression "." identifier
                   / identifier function-arguments
                   / postfix-expression "." identifier function-arguments
                   / named-type "::" identifier function-arguments ; this used to be a circuit-type
                   / named-type "::" identifier ; this is new to allow static members on 
                   / postfix-expression "[" expression "]"
                   / postfix-expression "[" [expression] ".." [expression] "]"

Now methods and static members would be first-class citizens of scalar types and their values. For example, the following could be done:

let x = 1u8.to_bits(); // A method call on on a scalar value itself
let x = u8::MAX; // A constant value on the scalar type
let y = u8::to_bits(1u8); // A static method on the scalar type

Drawbacks

This change adds more complexity to the language.

Effect on Ecosystem

None. The new parsing changes would not break any older programs.

Alternatives

None.

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