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Optional stack-effect checking and basic type discipline #68

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Open
Optional stack-effect checking and basic type discipline#68
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enhancementNew feature or request

Description

@tetsuo-cpp
tetsuo-cpp
opened on Aug 9, 2026

Summary

Add optional verification that stack depth (and, where known, int vs float bit-interpretation) is consistent at control-flow merges and word boundaries.

Motivation

The stack is intentionally untyped (!forth.stack as i64 cells; floats are bit patterns). The programmer ensures type safety. That is flexible but makes mistakes silent: using + instead of F+, or unbalanced IF branches that leave different depths, often produce wrong results rather than compile errors.

Control-flow structure is already validated (#21). Stack effects are not.

Proposed levels

Level 1 — Depth checking (high value, do first)

  • Annotate or infer stack depth delta per word/op
  • Require matching depths on IF/ELSE arms, loop back-edges, and word exit points
  • Error: IF branches leave different stack depths (then=2, else=1)

Level 2 — Optional sort tracking

  • Track a coarse tag per slot: int / float / addr / unknown
  • Warn or error on F+ consuming int, + consuming float, etc.
  • Escape hatch: explicit bitcast words or UNSAFE regions

Level 3 — Effect comments as checked contracts (optional)

: dot ( addr addr n -- f ) ... ;

Parse stack comments and verify against inferred effects (Forth tradition).

Acceptance criteria

  • Depth checker behind a flag or on-by-default for obvious imbalances
  • LIT tests for unbalanced IF/loop/word effects
  • Document inference rules and false-positive policy
  • (Stretch) coarse int/float warnings

Non-goals

  • Full dependent types or MLIR type redesign of !forth.stack in v1
  • Runtime type tags on the GPU stack

Related

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Optional stack-effect checking and basic type discipline · Issue #68 · tetsuo-cpp/warpforth · GitHub
      Skip to content
      Optional stack-effect checking and basic type discipline #68
      Open
      Open
      Optional stack-effect checking and basic type discipline#68
      Labels
      enhancementNew feature or request
      Description
      @tetsuo-cpp
      tetsuo-cpp
      opened on Aug 9, 2026
      Summary
      Add optional verification that stack depth (and, where known, int vs float bit-interpretation) is consistent at control-flow merges and word boundaries.
      Motivation
      The stack is intentionally untyped (!forth.stack as i64 cells; floats are bit patterns). The programmer ensures type safety. That is flexible but makes mistakes silent: using + instead of F+, or unbalanced IF branches that leave different depths, often produce wrong results rather than compile errors.
      Control-flow structure is already validated (#21). Stack effects are not.
      Proposed levels
      Level 1 — Depth checking (high value, do first)
      • Annotate or infer stack depth delta per word/op
      • Require matching depths on IF/ELSE arms, loop back-edges, and word exit points
      • Error: IF branches leave different stack depths (then=2, else=1)
      Level 2 — Optional sort tracking
      • Track a coarse tag per slot: int / float / addr / unknown
      • Warn or error on F+ consuming int, + consuming float, etc.
      • Escape hatch: explicit bitcast words or UNSAFE regions
      Level 3 — Effect comments as checked contracts (optional)
      : dot ( addr addr n -- f ) ... ;
      Parse stack comments and verify against inferred effects (Forth tradition).
      Acceptance criteria
      •  Depth checker behind a flag or on-by-default for obvious imbalances
      •  LIT tests for unbalanced IF/loop/word effects
      •  Document inference rules and false-positive policy
      •  (Stretch) coarse int/float warnings
      Non-goals
      • Full dependent types or MLIR type redesign of !forth.stack in v1
      • Runtime type tags on the GPU stack
      Related
      Metadata
      Metadata
      Assignees
      No one assigned
        Labels
        enhancementNew feature or request
        Projects
        No projects
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          No milestone
          Relationships
          None yet
          Development
          No branches or pull requests
          Issue actions
          
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Optional stack-effect checking and basic type discipline · Issue #68 · tetsuo-cpp/warpforth · GitHub
          Skip to content
          Optional stack-effect checking and basic type discipline #68
          Open
          Open
          Optional stack-effect checking and basic type discipline#68
          Labels
          enhancementNew feature or request
          Description
          @tetsuo-cpp
          tetsuo-cpp
          opened on Aug 9, 2026
          Summary
          Add optional verification that stack depth (and, where known, int vs float bit-interpretation) is consistent at control-flow merges and word boundaries.
          Motivation
          The stack is intentionally untyped (!forth.stack as i64 cells; floats are bit patterns). The programmer ensures type safety. That is flexible but makes mistakes silent: using + instead of F+, or unbalanced IF branches that leave different depths, often produce wrong results rather than compile errors.
          Control-flow structure is already validated (#21). Stack effects are not.
          Proposed levels
          Level 1 — Depth checking (high value, do first)
          • Annotate or infer stack depth delta per word/op
          • Require matching depths on IF/ELSE arms, loop back-edges, and word exit points
          • Error: IF branches leave different stack depths (then=2, else=1)
          Level 2 — Optional sort tracking
          • Track a coarse tag per slot: int / float / addr / unknown
          • Warn or error on F+ consuming int, + consuming float, etc.
          • Escape hatch: explicit bitcast words or UNSAFE regions
          Level 3 — Effect comments as checked contracts (optional)
          : dot ( addr addr n -- f ) ... ;
          Parse stack comments and verify against inferred effects (Forth tradition).
          Acceptance criteria
          •  Depth checker behind a flag or on-by-default for obvious imbalances
          •  LIT tests for unbalanced IF/loop/word effects
          •  Document inference rules and false-positive policy
          •  (Stretch) coarse int/float warnings
          Non-goals
          • Full dependent types or MLIR type redesign of !forth.stack in v1
          • Runtime type tags on the GPU stack
          Related
          Metadata
          Metadata
          Assignees
          No one assigned
            Labels
            enhancementNew feature or request
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(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Optional stack-effect checking and basic type discipline · Issue #68 · tetsuo-cpp/warpforth · GitHub
              Skip to content
              Optional stack-effect checking and basic type discipline #68
              Open
              Open
              Optional stack-effect checking and basic type discipline#68
              Labels
              enhancementNew feature or request
              Description
              @tetsuo-cpp
              tetsuo-cpp
              opened on Aug 9, 2026
              Summary
              Add optional verification that stack depth (and, where known, int vs float bit-interpretation) is consistent at control-flow merges and word boundaries.
              Motivation
              The stack is intentionally untyped (!forth.stack as i64 cells; floats are bit patterns). The programmer ensures type safety. That is flexible but makes mistakes silent: using + instead of F+, or unbalanced IF branches that leave different depths, often produce wrong results rather than compile errors.
              Control-flow structure is already validated (#21). Stack effects are not.
              Proposed levels
              Level 1 — Depth checking (high value, do first)
              • Annotate or infer stack depth delta per word/op
              • Require matching depths on IF/ELSE arms, loop back-edges, and word exit points
              • Error: IF branches leave different stack depths (then=2, else=1)
              Level 2 — Optional sort tracking
              • Track a coarse tag per slot: int / float / addr / unknown
              • Warn or error on F+ consuming int, + consuming float, etc.
              • Escape hatch: explicit bitcast words or UNSAFE regions
              Level 3 — Effect comments as checked contracts (optional)
              : dot ( addr addr n -- f ) ... ;
              Parse stack comments and verify against inferred effects (Forth tradition).
              Acceptance criteria
              •  Depth checker behind a flag or on-by-default for obvious imbalances
              •  LIT tests for unbalanced IF/loop/word effects
              •  Document inference rules and false-positive policy
              •  (Stretch) coarse int/float warnings
              Non-goals
              • Full dependent types or MLIR type redesign of !forth.stack in v1
              • Runtime type tags on the GPU stack
              Related
              Metadata
              Metadata
              Assignees
              No one assigned
                Labels
                enhancementNew feature or request
                Projects
                No projects
                  Milestone
                  No milestone
                  Relationships
                  None yet
                  Development
                  No branches or pull requests
                  Issue actions
                  
, 'i');
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(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
Optional stack-effect checking and basic type discipline · Issue #68 · tetsuo-cpp/warpforth · GitHub
                  Skip to content
                  Optional stack-effect checking and basic type discipline #68
                  Open
                  Open
                  Optional stack-effect checking and basic type discipline#68
                  Labels
                  enhancementNew feature or request
                  Description
                  @tetsuo-cpp
                  tetsuo-cpp
                  opened on Aug 9, 2026
                  Summary
                  Add optional verification that stack depth (and, where known, int vs float bit-interpretation) is consistent at control-flow merges and word boundaries.
                  Motivation
                  The stack is intentionally untyped (!forth.stack as i64 cells; floats are bit patterns). The programmer ensures type safety. That is flexible but makes mistakes silent: using + instead of F+, or unbalanced IF branches that leave different depths, often produce wrong results rather than compile errors.
                  Control-flow structure is already validated (#21). Stack effects are not.
                  Proposed levels
                  Level 1 — Depth checking (high value, do first)
                  • Annotate or infer stack depth delta per word/op
                  • Require matching depths on IF/ELSE arms, loop back-edges, and word exit points
                  • Error: IF branches leave different stack depths (then=2, else=1)
                  Level 2 — Optional sort tracking
                  • Track a coarse tag per slot: int / float / addr / unknown
                  • Warn or error on F+ consuming int, + consuming float, etc.
                  • Escape hatch: explicit bitcast words or UNSAFE regions
                  Level 3 — Effect comments as checked contracts (optional)
                  : dot ( addr addr n -- f ) ... ;
                  Parse stack comments and verify against inferred effects (Forth tradition).
                  Acceptance criteria
                  •  Depth checker behind a flag or on-by-default for obvious imbalances
                  •  LIT tests for unbalanced IF/loop/word effects
                  •  Document inference rules and false-positive policy
                  •  (Stretch) coarse int/float warnings
                  Non-goals
                  • Full dependent types or MLIR type redesign of !forth.stack in v1
                  • Runtime type tags on the GPU stack
                  Related
                  Metadata
                  Metadata
                  Assignees
                  No one assigned
                    Labels
                    enhancementNew feature or request
                    Projects
                    No projects
                      Milestone
                      No milestone
                      Relationships
                      None yet
                      Development
                      No branches or pull requests
                      Issue actions
                      
, 'i');
if (__m === '*' || __re.test(location.href)) {
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function tryTheater() {
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})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Optional stack-effect checking and basic type discipline · Issue #68 · tetsuo-cpp/warpforth · GitHub
                      Skip to content
                      Optional stack-effect checking and basic type discipline #68
                      Open
                      Open
                      Optional stack-effect checking and basic type discipline#68
                      Labels
                      enhancementNew feature or request
                      Description
                      @tetsuo-cpp
                      tetsuo-cpp
                      opened on Aug 9, 2026
                      Summary
                      Add optional verification that stack depth (and, where known, int vs float bit-interpretation) is consistent at control-flow merges and word boundaries.
                      Motivation
                      The stack is intentionally untyped (!forth.stack as i64 cells; floats are bit patterns). The programmer ensures type safety. That is flexible but makes mistakes silent: using + instead of F+, or unbalanced IF branches that leave different depths, often produce wrong results rather than compile errors.
                      Control-flow structure is already validated (#21). Stack effects are not.
                      Proposed levels
                      Level 1 — Depth checking (high value, do first)
                      • Annotate or infer stack depth delta per word/op
                      • Require matching depths on IF/ELSE arms, loop back-edges, and word exit points
                      • Error: IF branches leave different stack depths (then=2, else=1)
                      Level 2 — Optional sort tracking
                      • Track a coarse tag per slot: int / float / addr / unknown
                      • Warn or error on F+ consuming int, + consuming float, etc.
                      • Escape hatch: explicit bitcast words or UNSAFE regions
                      Level 3 — Effect comments as checked contracts (optional)
                      : dot ( addr addr n -- f ) ... ;
                      Parse stack comments and verify against inferred effects (Forth tradition).
                      Acceptance criteria
                      •  Depth checker behind a flag or on-by-default for obvious imbalances
                      •  LIT tests for unbalanced IF/loop/word effects
                      •  Document inference rules and false-positive policy
                      •  (Stretch) coarse int/float warnings
                      Non-goals
                      • Full dependent types or MLIR type redesign of !forth.stack in v1
                      • Runtime type tags on the GPU stack
                      Related
                      Metadata
                      Metadata
                      Assignees
                      No one assigned
                        Labels
                        enhancementNew feature or request
                        Projects
                        No projects
                          Milestone
                          No milestone
                          Relationships
                          None yet
                          Development
                          No branches or pull requests
                          Issue actions
                          
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(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Optional stack-effect checking and basic type discipline · Issue #68 · tetsuo-cpp/warpforth · GitHub
                          Skip to content
                          Optional stack-effect checking and basic type discipline #68
                          Open
                          Open
                          Optional stack-effect checking and basic type discipline#68
                          Labels
                          enhancementNew feature or request
                          Description
                          @tetsuo-cpp
                          tetsuo-cpp
                          opened on Aug 9, 2026
                          Summary
                          Add optional verification that stack depth (and, where known, int vs float bit-interpretation) is consistent at control-flow merges and word boundaries.
                          Motivation
                          The stack is intentionally untyped (!forth.stack as i64 cells; floats are bit patterns). The programmer ensures type safety. That is flexible but makes mistakes silent: using + instead of F+, or unbalanced IF branches that leave different depths, often produce wrong results rather than compile errors.
                          Control-flow structure is already validated (#21). Stack effects are not.
                          Proposed levels
                          Level 1 — Depth checking (high value, do first)
                          • Annotate or infer stack depth delta per word/op
                          • Require matching depths on IF/ELSE arms, loop back-edges, and word exit points
                          • Error: IF branches leave different stack depths (then=2, else=1)
                          Level 2 — Optional sort tracking
                          • Track a coarse tag per slot: int / float / addr / unknown
                          • Warn or error on F+ consuming int, + consuming float, etc.
                          • Escape hatch: explicit bitcast words or UNSAFE regions
                          Level 3 — Effect comments as checked contracts (optional)
                          : dot ( addr addr n -- f ) ... ;
                          Parse stack comments and verify against inferred effects (Forth tradition).
                          Acceptance criteria
                          •  Depth checker behind a flag or on-by-default for obvious imbalances
                          •  LIT tests for unbalanced IF/loop/word effects
                          •  Document inference rules and false-positive policy
                          •  (Stretch) coarse int/float warnings
                          Non-goals
                          • Full dependent types or MLIR type redesign of !forth.stack in v1
                          • Runtime type tags on the GPU stack
                          Related
                          Metadata
                          Metadata
                          Assignees
                          No one assigned
                            Labels
                            enhancementNew feature or request
                            Projects
                            No projects
                              Milestone
                              No milestone
                              Relationships
                              None yet
                              Development
                              No branches or pull requests
                              Issue actions
                              
, 'i');
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var enabled = true;
function applyDarkMode() {
if (!enabled) return;
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style.id = 'universal-dark-mode-style';
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::-webkit-scrollbar-thumb { background: #444 !important; }
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::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
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function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
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if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
} else {
removeDarkMode();
console.log('[Universal Dark Mode] Disabled');
}
}
});
// Apply on load
applyDarkMode();
// Re-apply on dynamic content
var observer = new MutationObserver(function(mutations) {
if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
}
});
observer.observe(document.head, { childList: true });
console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
})();
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();
Optional stack-effect checking and basic type discipline · Issue #68 · tetsuo-cpp/warpforth · GitHub
                              Skip to content
                              Optional stack-effect checking and basic type discipline #68
                              Open
                              Open
                              Optional stack-effect checking and basic type discipline#68
                              Labels
                              enhancementNew feature or request
                              Description
                              @tetsuo-cpp
                              tetsuo-cpp
                              opened on Aug 9, 2026
                              Summary
                              Add optional verification that stack depth (and, where known, int vs float bit-interpretation) is consistent at control-flow merges and word boundaries.
                              Motivation
                              The stack is intentionally untyped (!forth.stack as i64 cells; floats are bit patterns). The programmer ensures type safety. That is flexible but makes mistakes silent: using + instead of F+, or unbalanced IF branches that leave different depths, often produce wrong results rather than compile errors.
                              Control-flow structure is already validated (#21). Stack effects are not.
                              Proposed levels
                              Level 1 — Depth checking (high value, do first)
                              • Annotate or infer stack depth delta per word/op
                              • Require matching depths on IF/ELSE arms, loop back-edges, and word exit points
                              • Error: IF branches leave different stack depths (then=2, else=1)
                              Level 2 — Optional sort tracking
                              • Track a coarse tag per slot: int / float / addr / unknown
                              • Warn or error on F+ consuming int, + consuming float, etc.
                              • Escape hatch: explicit bitcast words or UNSAFE regions
                              Level 3 — Effect comments as checked contracts (optional)
                              : dot ( addr addr n -- f ) ... ;
                              Parse stack comments and verify against inferred effects (Forth tradition).
                              Acceptance criteria
                              •  Depth checker behind a flag or on-by-default for obvious imbalances
                              •  LIT tests for unbalanced IF/loop/word effects
                              •  Document inference rules and false-positive policy
                              •  (Stretch) coarse int/float warnings
                              Non-goals
                              • Full dependent types or MLIR type redesign of !forth.stack in v1
                              • Runtime type tags on the GPU stack
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