📐mlab-parser

The groupant beside mlab/src/parser.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.

Facts

Components

Obernants

The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.

Parts

• mlab-parser-expression-precedence

Model text

descriptant

Recursive precedence and statement parser

parse_program lexes then descends statements. Functions partition into Program.functions. LHS probing restores position when no assignment follows. Power is left-associated: 2^3^2 maps Pow(Pow(2,3),2); unary wraps power: -2^2 maps Neg(Pow(2,2)). Matrix whitespace before unspaced sign starts a new element; end is special only with positive index_depth.

Modeling epoch 2026-10-31

Prospective source reading precedes test additions. Retained observations: lexer space_before and Newline feed matrix and statement boundaries; AST tags are consumed by interp/vm. end resolution belongs to interpreter index context, not a parser numeric substitution; n-dimensional shape checks remain downstream.

This is partial source-derived modeling, not proof, full semantic coverage, or a performance result. Public malformed representations, unbounded allocations and exhaustive numerical edge cases remain outside the checked fixtures.

approximant

Recursive precedence and statement parser forward relation

parse_program lexes then descends statements. Functions partition into Program.functions. LHS probing restores position when no assignment follows. Power is left-associated: 2^3^2 maps Pow(Pow(2,3),2); unary wraps power: -2^2 maps Neg(Pow(2,2)). Matrix whitespace before unspaced sign starts a new element; end is special only with positive index_depth.

Domain: Lexer-accepted token stream; recursive stack/allocation resources. No external files/evaluation. Function bodies may terminate at EOF/next function; ordinary blocks require matching terminator.

No executable Rust surrogate is supplied: categorical decisions require exact observations; numerical kernels have no measured approximation metric here. Future supported caps are 1%, 2%, 5%, 10% only.

invariant

Invariant and cost

Ordered statement bodies, explicit Paren nodes, optional range step and index arguments survive parsing. Empty input gives empty Program. Anonymous body resets index_depth and restores matrix context only on successful descent; failed parser state is discarded by parse_program.

Cost: O(T) ordinary descent plus speculative LHS parse/reparse; deeply nested indexed LHS probes can add repeated subexpression work, so no uniform linear proof. O(T) retained AST plus recursion depth; no nesting cap.

Failure ordering: Whole lexing precedes syntax errors. Statement keyword/command/increment dispatch precedes LHS probing then expression fallback. Missing block terminator reports first expected term; unsupported global/persistent fails before runtime.

composition

Parent composition

lexer space_before and Newline feed matrix and statement boundaries; AST tags are consumed by interp/vm. end resolution belongs to interpreter index context, not a parser numeric substitution; n-dimensional shape checks remain downstream.

Scoped fragments are projections over exact byte intervals in this source; they share one parent syntax projection. Uncovered declarations and embedded checks remain parent modeled. Whole lexing precedes syntax errors. Statement keyword/command/increment dispatch precedes LHS probing then expression fallback. Missing block terminator reports first expected term; unsupported global/persistent fails before runtime.

The relation is source-derived and finite checks cannot establish complete correctness or a composition-wide numerical error bound.

models

behavior_complement

The accepted parse relation excludes right-associated 2^3^2, flattening [1 -2] to subtraction, accepting naked end as expression, or returning a partially built Program on Result::Err. It does not exclude semantically invalid break, unknown function, public invalid AST or runtime division by zero.

reverse_reconstruction

P^-1(tree) contains texts sharing AST tags/literals and retained statement line/print flags; comments and many separators are ambiguous. For Pow(Pow(2,3),2), 2^3^2 is compatible; 2^(3^2) differs through Paren and tree shape. An evaluated scalar has much larger fibers.

representation_transport

Ordered statement bodies, explicit Paren nodes, optional range step and index arguments survive parsing. Empty input gives empty Program. Anonymous body resets index_depth and restores matrix context only on successful descent; failed parser state is discarded by parse_program.

failure_precedence

Whole lexing precedes syntax errors. Statement keyword/command/increment dispatch precedes LHS probing then expression fallback. Missing block terminator reports first expected term; unsupported global/persistent fails before runtime.

resource_domain

Lexer-accepted token stream; recursive stack/allocation resources. No external files/evaluation. Function bodies may terminate at EOF/next function; ordinary blocks require matching terminator.

interaction_relation

lexer space_before and Newline feed matrix and statement boundaries; AST tags are consumed by interp/vm. end resolution belongs to interpreter index context, not a parser numeric substitution; n-dimensional shape checks remain downstream.

tests

Source-specific bounded evidence

parser::wave30::precedence: left power association, unary precedence, matrix whitespace, End context, missing block terminator, empty program.

Seven named tests each passed twice debug and twice release on 2026-10-31, with actual named log lines sorted and identical across all four runs (28 selected successful executions). Each source has a compiled changed-assertion negative control; six runtime sources additionally have compiled production-body mutants that fail those unchanged tests. AST has representation evidence only. Every mutant is byte-restored and its positive test rerun. See evidence.json for this source's exact hash, mutation and exit statuses. External receipts retain full logs, command metadata, control records and prospective notes.

Unexecuted here: No exhaustive statement/function/control grammar. No corpus, GPU, live filesystem, timer or callback run. No broad Clippy claim; dependency/style checks were not repeated. Only appended test blocks were rustfmt-formatted; original production bytes are unchanged.

This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/mlab/src/parser.rs.groupant/