expanded class DISPEXP\n -- Disposable and expanded\ninsert DISPOSABLE\n redefine out end\nfeature {ANY}\n name: STRING\n value: INTEGER\n out: STRING\n do\n if name\/=Void then\n Result := "DISPEXP"+name+" "+value.out\n else\n Result := "nameless DISPEXP"\n end\nend\nfeature {} \n dispose \n do \n print("disposing DISPEXP")\n end\n \nend<\/code><\/pre>\n\n\n\ndoesn’t work as the compiler says that <\/p>\n\n\n\n
****** Error: Invalid usage of feature `to_pointer' of class ANY. (The target which is of type DISPEXP cannot be converted to a memory address.)\n\nThe source lines relevant to this message are the following:\n\nLine 421 column 4 in ANY (\/home\/paolo\/src\/liberty-eiffel\/src\/lib\/kernel\/any.e):\n to_pointer: POINTER\n ^ \nLine 8 column 16 in DISPEXPEX (\/home\/paolo\/tmp\/dispexpex.e):\n print(a.to_pointer.out)<\/pre>\n\n\n\nMost programmers would have already rejected Eiffel by now. First of all why – for Heaven sake – doesn’t to_pointer have a require not is_expanded? <\/p>\n\n\n\n
The answer is simple: ANY does not have an is_expanded or a is_reference feature. At first I was going to write it as <\/p>\n\n\n\n
is_expanded: BOOLEAN do Result := <\/p>\n\n\n\n
instead it seems that introspection – i.e the usage of internals which require explicit support from the compiler – is not required as it can be implemented as <\/p>\n\n\n\n
is_expanded: BOOLEAN local like_current: like Current do Result := like_current \/= Void end<\/p>\n\n\n\n
but it cannot work. In fact the compiler (correctly) argues that<\/p>\n\n\n\n
****** Error: Such a weird comparison with Void is not allowed because it would be always True. (See explaination below.)\n\nLine 21 column 27 in DISPEXP (\/home\/paolo\/tmp\/dispexp.e):\n Result := like_current \/= Void\n ^ \n------\n****** Fatal Error: The declaration type of `like_current' is obviously expanded (i.e. the written type mark is \"DISPEXP\"). You can use the Void comparison only when other type mark is a reference type or, if it is an expanded type, it must be an anchor or some formal generic argument. Fix this error first.<\/pre>\n\n\n\nSo in the end one could write ANY’s is_expanded as<\/p>\n\n\n\n
is_expanded: BOOLEAN do Result := to_interals.type_is_expanded end<\/code><\/pre>\n\n\n\nthat implies that a simple class such as DISPEXP must insert INTERNALS_HANDLER. <\/p>\n\n\n\n
So now we understand why to_pointer<\/strong> is built not to even compile when used on expanded values. It is a simplification that made life quite simpler to implementors.<\/p>\n\n\n\nThere’s a issue. Why did they add “to_pointer<\/strong>” at all? You may promptly answer: because you need it to interact with low-level code. But we do have the $<\/strong> operator for this. And wonder of wonders, it works smoothly on expanded objects. But it is meant to be used on the final name of a feature which is not a constant attribute or by the name of some local variable. Not even Current<\/strong>. If it wasn’t for the latter limitation one could write to_pointer: POINTER do Result := $Current end<\/strong> <\/p>\n\n\n\n<\/p>\n\n\n\n
… more on this later<\/p>\n","protected":false},"excerpt":{"rendered":"
Note: I wrote this notes on august 2021, but I shall publish them now in the state thay are otherwise I will lose memory of their existence yet another time… Lately I discovered that Liberty Eiffel needs expanded classes to be DISPOSABLE to get rid of a garbage collector like Rust does. So I was…<\/p>\n
Read more →<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":4,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"","footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[1],"tags":[],"class_list":["post-8615","post","type-post","status-publish","format-standard","hentry","category-senza-categoria"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p6daft-2eX","jetpack-related-posts":[{"id":6836,"url":"https:\/\/monodes.com\/predaelli\/2020\/03\/06\/what-is-faster-in-c-a-struct-or-a-class-c-architects-medium\/","url_meta":{"origin":8615,"position":0},"title":"What Is Faster In C#: A Struct Or A Class? – C# Architects – Medium","author":"Paolo Redaelli","date":"2020-03-06","format":false,"excerpt":"What do you think is faster: filling an array with one million structs, or filling an array with one million classes? Mark Farragher ask himself What Is Faster In C#: A Struct Or A Class? - C# Architects - on Medium. But of course the third version is faster because\u2026","rel":"","context":"In "Documentations"","block_context":{"text":"Documentations","link":"https:\/\/monodes.com\/predaelli\/category\/documentations\/"},"img":{"alt_text":"Mark Farragher","src":"https:\/\/i0.wp.com\/monodes.com\/predaelli\/wp-content\/uploads\/sites\/4\/2020\/03\/1IyCy3Cj8Kuv759UIaFq3aw.jpeg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":8612,"url":"https:\/\/monodes.com\/predaelli\/2022\/05\/30\/eiffel-rust-and-memory-management\/","url_meta":{"origin":8615,"position":1},"title":"Eiffel, Rust and memory management","author":"Paolo Redaelli","date":"2022-05-30","format":false,"excerpt":"It already passed one year almost two years since in \"Oh my lazyness!\" when I wrote I shall restart my efforts on Liberty EIffel and Monodes\u2026 \ud83d\ude41 I hope to integrate them in my current effort. 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I nemici della Chiesa sono invece tolleranti sui principi, perch\u00e9 non credono, ma intransigenti nella pratica, perch\u00e9 non amano. La Chiesa assolve i peccatori, i nemici della Chiesa assolvono i peccati.da p. Reginald Garrigou-Lagrange, Dieu, son\u2026","rel":"","context":"In "Senza categoria"","block_context":{"text":"Senza categoria","link":"https:\/\/monodes.com\/predaelli\/category\/senza-categoria\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":15164,"url":"https:\/\/monodes.com\/predaelli\/2026\/02\/25\/memory-constraints\/","url_meta":{"origin":8615,"position":4},"title":"Memory constraints","author":"Paolo Redaelli","date":"2026-02-25","format":false,"excerpt":"The RAM shortage might be the best thing to happen in software development in years For years, the answer was simple: throw more RAM at it. 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