Opal is fun. I have a few simplifications to propose for the AST->BC OCASTTranslator 1) instead of testing isEffectTranslator or refining in subclass, most often we could just let self visit the node. Indeed, self will already be either a Translator ForEffect or ForValue. For example, this could apply to emitIfFalseIfTrue: emitIfNilIfNotNil: visitCascadeNode: This might also remove a few useless pushNil; pop BC sequences. 2) I think we can simplify the #visitBlockNode: / #visitSequenceNode: pair. Indeed, visitSequenceNode: tests if its parent isBlock, and if so will emitValue, else emitEffect. Inversely visitBlockNode: always ask to emitEffect, but since it contains a SequenceNode, this is a big lie. I suggest to always let the valueTranslator emitValue visitBlockNode: and simplify #visitSequenceNode: to just let (self visitNode: statements last). 3) I suggest changing the BC generated for or: and and: instead of: valueTranslator visitNode: aMessageNode receiver. methodBuilder jumpAheadTo: #else if: false; pushLiteral: true; jumpAheadTo: #end; jumpAheadTarget: #else. valueTranslator visitInlinedBlockNode: aMessageNode arguments first. methodBuilder jumpAheadTarget: #end. We could just use dup and thus remove a jump: valueTranslator visitNode: aMessageNode receiver. methodBuilder pushDup; jumpAheadTo: #end if: true; popTop. self visitInlinedBlockNode: aMessageNode arguments first. methodBuilder jumpAheadTarget: #end. ForEffect, this would just be self emitIfFalse: aMessageNode Of course, that last change might disturb the Decompiler a bit, but since we care far less now... I can open 1 or more issues if there is an interest. Nicolas