mpl/ISSUE_M0_BLOCKERS.md

🚀 Lock lexical & grammar spec for M0

Overview

This issue tracks the resolution of three critical blockers that must be decided before implementing the ANTLR 4 grammar for MPL. These decisions are required to ensure the lexer can be implemented without surprises and that all M0 exit criteria are objectively testable.

Blockers

1. Comment Syntax 🚫

Status: MISSING
Decision needed by: Before lexer PR is merged
Rationale: Source files cannot compile without comment support

Options to consider:

• -- till EOL (Ada/Haskell style)
• /* ... */ (C style)
• # till EOL (Python/Ruby style)
• Support for both single-line and multi-line comments

Recommendation: Use -- for single-line and {- ... -} for multi-line (Haskell-style) to align with functional paradigm

2. String Literal Rules ⚠️

Status: INCOMPLETE
Decision needed by: Before lexer PR is merged
Rationale: Required for hello-world sample

Decisions needed:

• Escape sequences: Standard set (\n, \t, \\, \") + Unicode (\u{1F600})
• String delimiters: Double quotes only or support for raw strings?
• Multi-line string support?
• String interpolation syntax (or defer to M1)?

Recommendation:

• Use "..." for regular strings with standard escapes
• Add """...""" for multi-line raw strings (no escapes)
• Defer interpolation to M1

3. Path Literal Fallback ⚠️

Status: INCOMPLETE
Decision needed by: Before lexer PR is merged
Rationale: 🖫 glyph may not render on all systems

Options:

• Make 🖫 required (pure Unicode approach)
• Add ASCII escape like @path"..." or #path"..."
• Use \path as the ASCII escape (consistent with other escapes)

Recommendation: Support both 🖫"..." and \path"..." for maximum compatibility

Additional Lexical Decisions

ASCII Escape Mapping

Need complete one-to-one table for all Unicode glyphs. Current partial list:

• \gamma → γ
• \lam or \lambda → λ
• \Rightarrow → ⇒
• etc.

Number Literal Format

• Decimal: 123, 123.456, 1.23e10
• Hex: 0x1A2B
• Binary: 0b1101
• Suffixes: _i32, _f64, _bigint (or defer to M1?)

Exit Criteria

Once this issue is closed, we can:

• Implement the lexer with confidence
• Parse all example programs
• Generate syntax highlighting for editors
• Create the glyph-escapes.md reference

Action Items

1. Make decisions on all three blockers
2. Update math_prog_lang.md with decisions
3. Create docs/lexical-spec.md with complete token rules
4. Tag specification as v0.1-alpha

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Assignee: @developtheweb
Labels: blocker, M0, specification, grammar