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Proposal: Modernizing XGo MiniSpec with Tuple Types

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xushiwei edited this page Jan 24, 2026 · 4 revisions

This proposal outlines the strategic refinement of the XGo specification to simplify the MiniSpec while maintaining full compatibility in the FullSpec. By replacing traditional Go-style structs with Tuples in the MiniSpec, XGo achieves a more cohesive, functional, and modern syntax.

Related files:

  • doc/spec-mini.md (MiniSpec)
  • doc/spec.md (FullSpec)
  • doc/spec/mini/mini.xgo (MiniSpec in EBNF Grammar)

Proposal: Modernizing XGo MiniSpec with Tuple Types

1. Overview

To enhance the simplicity and functional elegance of the XGo MiniSpec, we propose removing traditional struct types and CompositeLit (brace-based initialization) from the core recommended syntax set. These will be replaced by Tuples, which serve as syntactic sugar for anonymous structs but use a more consistent function-style construction.

MiniSpec becomes more focused on modern, lightweight data composition.

FullSpec retains all traditional Go-style struct capabilities for backward compatibility and complex system definitions.

2. Changes to MiniSpec

The MiniSpec will undergo the following structural changes:

A. Removal of Structs and Braced Literals

  • StructType is removed from MiniSpec and moved to FullSpec.
  • CompositeLit (e.g., Type{fields...}) is removed from MiniSpec and moved to FullSpec.
  • Struct-style Tuple Construction (using {}) is relegated to FullSpec.

B. Introduction of Tuple Types

Tuples are introduced as the primary way to define structured data.

  • Type Declaration:
type Point (x, y int) // Named Tuple
type Result (int, error) // Anonymous Tuple
  • Single-Element Degeneracy: (T) is equivalent to T.

C. Function-Style Construction (MiniSpec Standard)

To unify the syntax for creating objects and calling functions, the MiniSpec will use the Function-Style Construction for Tuples:

  • Positional Construction: p := Point(10, 20)
  • Keyword Arguments (kwargs): p := Point(x = 10, y = 20) (Using = to distinguish from CompositeLit-style : used in FullSpec).

D. Anonymous Tuple Construction

Anonymous tuples can be constructed using parenthesized expressions:

  • t := (10, "hello", true)

E. Explicit Field Access

  • x := p.x (Named field)
  • val := t.0, name := t.1 (Numeric index)

3. Changes to FullSpec

The FullSpec will act as the superset, incorporating the removed MiniSpec elements and advanced Tuple features.

A. Preservation of Legacy Syntax

  • StructType: Standard struct { ... } remains valid.
  • CompositeLit: Brace-based initialization T{...} remains valid for both Structs and Tuples.

B. Advanced Tuple Features

  • Struct-style Construction: The ability to initialize a Tuple using braces (e.g., Point{x: 10, y: 20}) is supported in FullSpec for developers migrating from Go.
  • Type Compatibility: Rules for structural equivalence between different Tuple names are defined here.
  • Reflection: Details on how Tuples map to X_0, X_1 ordinal fields at runtime.
  1. Summary Table of Syntax Migration
Feature MiniSpec (New) FullSpec (Legacy/Advanced)
Data Grouping Tuples (x, y int) Structs & Tuples
Value Creation Function-style T(1, 2) Braced-style T{1, 2}
Keyword Args = syntax: T(x=1) : syntax: T{x:1}
Anon. Construction (1, "a") N/A (Handled as anon. struct)
Field Access .0 or .name .X_0, .0, or .name

4. Updated mini.xgo (EBNF Grammar)

The following represents the updated mini.xgo logic, replacing StructType and CompositeLit with TupleType and TupleConstruction logic.

// --- Updated XGo MiniSpec Grammar Snippet ---

// 1. Replace StructType with TupleType in TypeLit
TypeLit = PointerType | ArrayType | MapType | FuncType | TupleType | InterfaceType

// 2. Define TupleType (Syntactic sugar for anonymous structs)
TupleType = "(" ?TupleParameterList ")"
TupleParameterList = IDENT % "," Type | ParameterList

// 3. Update PrimaryExpr to handle Function-Style Construction
// CompositeLit is removed; Tuple values are created via CallOrConversion
PrimaryExpr = Operand *(CallOrConversion | SelectorOrTypeAssertion | IndexOrSlice | ErrWrap)

// 4. Update Operand to include Anonymous Tuple Construction
Operand = 
    INT ?UNIT | FLOAT ?UNIT | STRING | CHAR | RAT | IMAG | 
    AnonymousTuple | FunctionLit | IDENT | ...

// 5. Define Anonymous Tuple
AnonymousTuple = "(" LambdaExpr % "," ")"

// 6. Update CallOrConversion to support Kwargs (= syntax)
CallOrConversion = "(" ?(ArgList) ?"..." ?"," ")"
ArgList = (LambdaExpr | Kwarg) % ","
Kwarg = IDENT "=" LambdaExpr

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