Edit: Mogun

== WARNING: INFO ON THIS PAGE IS EXTREMLY OUTDATED. LEFT FOR HISTORICAL PURPOSES ONLY == Mogun is Factor-inspired and Factor-hosted language and is currently in early design stage. Its primary target is low-level speed-critical tasks, which you do not normally write on Factor itself (cell tags, GC, etc). Core of its design is programmer-friendly static typing with transparent and precise control over any compiler optimizations. Possibly, it's going to be LLVM-backended. === Basic Principles (UNDER CONSTRUCTION) === ==== Local stack shuffling ==== Only local stack shuffling primitive is %( .. )% syntax. It can rearrange and name any constant number of top stack elements. All other simple shufflers and combinators are normal words: [{: drop ( >X ) ; : dup ( <X X ) ; : swap ( <Y X >Y ) ; : dip -- ( >X QUOT ) call X ; : keep -- ( X QUOT ) call X ; : 2drop drop drop ; : 2dip -- swap [ dip ] dip ; : bi -- [ keep ] dip call ; : bi* -- [ dip ] dip call ; : bi@ -- dup bi* ;}] In combinators defititions you can see %--% word, which do not appear in shufflers. This word is unusual for Factor and its function will be described later. ==== Type-system ==== In Mogun any element on stack belongs to one of statically-distinguished class hierarhies. Inside each hierarhy classes can be statically or dynamically converted to each other. Classes can have additional slots with optimization-assisting values, avaliable at compile-time. Class from one hierarhy can simulate behaviour of other hierarhy, and can be used in its place. [{CLASS: integer { min -inf } { max +inf } ; CLASS: uint ? integer { min 0 } ; CLASS: sgn ; CLASS: positive < sgn ; CLASS: zero < sgn ; CLASS: negative < sgn ; MIMIC: integer sgn CLASS: fixed bitcount ; CLASS: ufixed = fixed ; CLASS: sfixed = fixed ; MIMIC: ufixed uint MIMIC: sfixed integer}] In this example you can see three class hierarhies: %integer%, %sgn% and %fixed%. Class %integer% describes any integer value between %min% and %max%. Class %uint% is an alias for class %integer% with %min% value set to %0%. Class %sgn% describes any number that can have sign. It can dynamically downcast to three subclasses: %positive%, %zero% and %negative%. %MIMIC: integer sgn% means that any %integer% value can be used everywhere, where %sgn% value or any its subclass is expected (obviously, because integers have sign). Class %fixed% describes bitfield of %bitcount% bits. Its value can be interpreted as unsigned or signed %integer%. Any %ufixed% and %sfixed% values can be converted to each other with static casting, and their usage in place of %integer% should generate different code. ==== Quotation semantics ==== Mogun quotation can be more complex then Factor one. It provides branching based on type-checking and in-place tail-cut recursion. For example, lets look at Mogun implementation of Factor %times% equivalent: [{: times -- swap :integer [ :positive -- [ [ call ] keep ] [ 1- ] bi* rec | :zero 2drop ] call ;}] Core loop of this word is divided by %|% symbol into two branches: - %:positive -- [ [ call ] keep ] [ 1- ] bi\* rec% - %:zero 2drop% Both branches start with type-checking - %:positive% and %:zero% words. This words are generated by %CLASS:% statement and do nothing, if top of the stack belongs to corresponding class, or raise type-checking error otherwise. First of this two branches is divided in two parts by %--% word: | %:positive% | type checking part before %--% (or whole branch if no %--% found, like in second branch) | %[ [ call ] keep ] [ 1- ] bi\* rec% | actual working part after %--% If quotation have more then one branch, in type checking part you can use only type-checking and stack-shuffling words. When %call%-ed, branch, that do not raise error in its type checking part, is selected for execution. Any errors, raised in actual working part of branch, lead to failing of whole %call%. At the end of the first branch you can see %rec% word. This is virtual symbol, used for in-place tail-cut recursion. After branch execution %call% checks top of the stack for %rec% symbol, and if it is found, removes it and %call%-s quotation again.

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