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Speaking of Lisp and Forth, I was really stunned when I noticed that adding syntactic support for "structs" in the language is about 10 lines in Forth (https://

by lukego 9y ago

Speaking of Lisp and Forth, I was really stunned when I noticed that adding syntactic support for "structs" in the language is about 10 lines in Forth (https://github.com/openbios/openfirmware/blob/master/forth/lib/struct.fth https://github.com/openbios/openfirmware/blob/master/forth/l...) and about 2000 lines in Lisp (https://github.com/sbcl/sbcl/blob/master/src/code/defstruct.lisp https://github.com/sbcl/sbcl/blob/master/src/code/defstruct....). Mitch Bradley wrote up an explanation of the Forth library, and lots of other cool bits of Openfirmware, at http://wiki.laptop.org/go/Forth_Lesson_18 http://wiki.laptop.org/go/Forth_Lesson_18.

kazinator 9y ago
You could also make some ten line hack to mock up structs in Lisp over a vector. That SBCL implementation has to conform to an ANSI standard. The TXR Lisp implementation of structs (the syntactic part) is 300 Lines: http://www.kylheku.com/cgit/txr/tree/share/txr/stdlib/struct.tl http://www.kylheku.com/cgit/txr/tree/share/txr/stdlib/struct... of which the defstruct macro is about half. The underlying implementation is in C: http://www.kylheku.com/cgit/txr/tree/struct.c http://www.kylheku.com/cgit/txr/tree/struct.c, which is some 1600 lines. TXR Lisp structs are an OOP system; they support inheritance, static and instance slots, inheritance of both, late injection of methods into a hierarchy and such. There is a fairly sophisticated initialization model and even support for C++-like RAII style. Structs are real objects that know their own type. They have a print and read representation, they know what slots they have and will reject invalid accesses and so on. You don't get something for nothing; the LOC's are spent for a reason. Looks like there is a tutorial on what appear to be these same Forth structs here: http://wiki.laptop.org/go/Forth_Lesson_18 http://wiki.laptop.org/go/Forth_Lesson_18 I don't see any example of how to create a struct, how to access it, how to show that two different struct types are incompatible, how accessing a field in a struct that it doesn't have results in an error, etc. It just looks like definitions of constants denoting offsets.

by lukego 9y ago

kazinator 9y ago

You could also make some ten line hack to mock up structs in Lisp over a vector. That SBCL implementation has to conform to an ANSI standard. The TXR Lisp implementation of structs (the syntactic part) is 300 Lines: http://www.kylheku.com/cgit/txr/tree/share/txr/stdlib/struct.tl http://www.kylheku.com/cgit/txr/tree/share/txr/stdlib/struct... of which the defstruct macro is about half. The underlying implementation is in C: http://www.kylheku.com/cgit/txr/tree/struct.c http://www.kylheku.com/cgit/txr/tree/struct.c, which is some 1600 lines. TXR Lisp structs are an OOP system; they support inheritance, static and instance slots, inheritance of both, late injection of methods into a hierarchy and such. There is a fairly sophisticated initialization model and even support for C++-like RAII style. Structs are real objects that know their own type. They have a print and read representation, they know what slots they have and will reject invalid accesses and so on. You don't get something for nothing; the LOC's are spent for a reason. Looks like there is a tutorial on what appear to be these same Forth structs here: http://wiki.laptop.org/go/Forth_Lesson_18 http://wiki.laptop.org/go/Forth_Lesson_18 I don't see any example of how to create a struct, how to access it, how to show that two different struct types are incompatible, how accessing a field in a struct that it doesn't have results in an error, etc. It just looks like definitions of constants denoting offsets.