L2: subroutines for DVM-BASIC — GOSUB/RETURN (fixes #102, stacks on #101) - #103
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L2: subroutines for DVM-BASIC — GOSUB/RETURN (fixes #102, stacks on #101)#103liqdmetal wants to merge 4 commits into
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…F/ELSE/ENDIF
Replaces GOTO-only spaghetti with structured loops and blocks (spec
dero-improvements-agenda.md L1, P0). Halves contract size, cuts the
len(scdata)*1.5 code-size fee term, makes contracts auditable.
New dvm/control_flow.go:
- FOR var = start TO end [STEP step] / NEXT var — counter loop, step
default 1, nested frames via the interpreter's Loops stack
- WHILE expr / WEND — pre-tested loop, jumps back to the WHILE line
- block IF expr THEN ... [ELSE ...] ENDIF — detected as the line ending
in THEN without GOTO (existing single-line IF THEN GOTO untouched)
- LoopFrame stack on DVM_Interpreter for nesting (FOR-in-WHILE verified)
- findMatchingLine scans forward for WEND/ENDIF respecting nesting
Consensus-safety:
- ALL new keywords gated on DVM version >= 10.0.0 (contract must call
version("10.0.0")); pre-fork contracts cannot accidentally use them
- no parser changes — the line-token interpreter dispatches the new
keywords natively
Tests (dvm/control_flow_test.go, 8 cases):
- FOR/NEXT sum(1..5)=15, FOR/STEP 0+2+4=6, WHILE countdown=10 iterations,
block IF/ELSE both branches, IF-no-ELSE fall-through, nested FOR-in-WHILE
total=9, version gate (1.2.3 rejected), no-version gate (0.0.0 rejected)
Full dvm suite green, whole tree builds.
…F/ELSE/ENDIF
Replaces GOTO-only spaghetti with structured loops and blocks (spec
dero-improvements-agenda.md L1, P0). Halves contract size, cuts the
len(scdata)*1.5 code-size fee term, makes contracts auditable.
New dvm/control_flow.go:
- FOR var = start TO end [STEP step] / NEXT var — counter loop, step
default 1, nested frames via the interpreter's Loops stack
- WHILE expr / WEND — pre-tested loop, jumps back to the WHILE line
- block IF expr THEN ... [ELSE ...] ENDIF — detected as the line ending
in THEN without GOTO (existing single-line IF THEN GOTO untouched)
- LoopFrame stack on DVM_Interpreter for nesting (FOR-in-WHILE verified)
- findMatchingLine scans forward for WEND/ENDIF respecting nesting
Consensus-safety:
- ALL new keywords gated on DVM version >= 10.0.0 (contract must call
version("10.0.0")); pre-fork contracts cannot accidentally use them
- no parser changes — the line-token interpreter dispatches natively
Tests (dvm/control_flow_test.go, 8 cases): FOR sum, FOR/STEP, WHILE
countdown, block IF/ELSE, IF-no-ELSE fall-through, nested FOR-in-WHILE,
version gate (1.2.3), no-version gate (0.0.0). All green.
Also carries the build-manifest fix (go.mod/go.sum) for fresh-clone builds.
The second P0 language item (spec dero-improvements-agenda.md L2): internal
subroutines so entrypoints stop re-implementing helpers.
GOSUB <line>: pushes the return address (the line after the GOSUB) onto
the interpreter's CallStack and jumps to <line>.
RETURN: when CallStack is non-empty, pops it and jumps back (subroutine
return — value ignored, subroutines communicate via shared Locals);
otherwise behaves exactly as today (function return). Fully
backward-compatible: existing contracts never push a CallStack.
Gated on DVM version >= 10.0.0 like L1 (contract must call
version("10.0.0")). Nests correctly (GOSUB-in-GOSUB, GOSUB-in-FOR).
Tests (dvm/control_flow_l2_test.go, 5 cases):
- TestL2_Gosub: shared-Locals helper (x*2)
- TestL2_NestedGosub: 1 + 10 = 11 via nested calls
- TestL2_GosubInFor: helper inside FOR body, 1+2+3 = 6
- TestL2_FunctionReturnStillWorks: plain RETURN unaffected
- TestL2_VersionGate: GOSUB at 1.2.3 rejected
Stacks on L1 (feature/dvm-l1-control-flow-pr, PR DEROFDN#101).
This was referenced Aug 23, 2026
…ndor) Same two fixes as the sibling PRs: remove the l.Operation.KickReader() calls (no published chzyer/readline implements it) and re-vendor with a proper modules.txt. Fresh-clone go build now succeeds without -mod=mod.
Author
|
Superseded by PR #126 — the consolidated language package. Same code, one reviewable PR with no vendor noise. |
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Summary
L2 from the DVM-BASIC language agenda (P0): subroutines via
GOSUB/RETURN— internal code reuse so entrypoints stop re-implementing helpers. Pairs with L1 structured control flow (PR #101): loops for repetition, subroutines for reuse.The syntax
Implementation
GOSUB <line>pushes the return address (the line after the GOSUB) onto the interpreter'sCallStackand jumps to<line>.RETURNpops theCallStackwhen non-empty (subroutine return — the value is ignored; subroutines communicate via sharedLocals) and jumps back; when the stack is empty it behaves exactly as today (function return with value).CallStack, so theirRETURNsemantics are untouched.Consensus safety
Gated on DVM version
>= 10.0.0like L1 — the contract must callversion("10.0.0"). Pre-fork contracts cannot accidentally use it.Tests (
dvm/control_flow_l2_test.go, 5 cases)TestL2_GosubTestL2_NestedGosubTestL2_GosubInForTestL2_FunctionReturnStillWorksTestL2_VersionGate1.2.3rejectedFull dvm suite green;
dvmpackage builds clean.Relationship
>=10.0.0gate, same interpreter mechanismBranch:
feature/dvm-l2-subroutinesin the forkliqdmetal/derohe-improvements-by-liqdmetal(stacked onfeature/dvm-l1-control-flow-pr). Carries the build-manifest fix.