| OBool | Sifflet.Language.Expr |
| OChar | Sifflet.Language.Expr |
| offsetTextBoxCenters | Sifflet.Data.TreeLayout |
| OFloat | Sifflet.Language.Expr |
| OInt | Sifflet.Language.Expr |
| on | Sifflet.UI.LittleGtk, Sifflet.UI |
| onDestroy | Sifflet.UI.LittleGtk, Sifflet.UI |
| OnEntryActivate | Sifflet.UI.Callback, Sifflet.UI |
| OnLayoutButtonPress | Sifflet.UI.Callback, Sifflet.UI |
| OnLayoutButtonRelease | Sifflet.UI.Callback, Sifflet.UI |
| OnLayoutExpose | Sifflet.UI.Callback, Sifflet.UI |
| OnLayoutMouseMove | Sifflet.UI.Callback, Sifflet.UI |
| OnMenuItemActivateLeaf | Sifflet.UI.Callback, Sifflet.UI |
| onSizeRequest | Sifflet.UI.LittleGtk, Sifflet.UI |
| OnWindowConfigure | Sifflet.UI.Callback, Sifflet.UI |
| OnWindowDestroy | Sifflet.UI.Callback, Sifflet.UI |
| OnWindowKeyPress | Sifflet.UI.Callback, Sifflet.UI |
| opAssoc | Sifflet.Foreign.Python |
| openNode | Sifflet.UI.Workspace, Sifflet.UI |
| opEq | Sifflet.Foreign.Python |
| opFDiv | Sifflet.Foreign.Python |
| opGe | Sifflet.Foreign.Python |
| opGt | Sifflet.Foreign.Python |
| opIDiv | Sifflet.Foreign.Python |
| opLe | Sifflet.Foreign.Python |
| opLt | Sifflet.Foreign.Python |
| opMinus | Sifflet.Foreign.Python |
| opMod | Sifflet.Foreign.Python |
| opName | Sifflet.Foreign.Python |
| opNe | Sifflet.Foreign.Python |
| opPlus | Sifflet.Foreign.Python |
| opPrec | Sifflet.Foreign.Python |
| opTimes | Sifflet.Foreign.Python |
| orderedChildren | Sifflet.Data.TreeGraph |
| orderedTreeToGraph | Sifflet.Data.TreeGraph |
| OStr | Sifflet.Language.Expr |
