2.0 syntax
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README.md
65
README.md
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@ -9,8 +9,7 @@ code).
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## Usage
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**TL;DR:** `[object slot-name]` is like `object.slotName` in C++, and
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`[object (.method args)]` is like `object.method(args)` in C++.
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**TL;DR:** `[object (method args)]` is like `object.method(args)` in C++.
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First, to enable `objective-lisp`'s syntax, just load the system:
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``` common-lisp
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@ -18,66 +17,44 @@ First, to enable `objective-lisp`'s syntax, just load the system:
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```
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`objective-lisp`'s syntax takes the form of a special S-expression, contained
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in square brackets rather than parentheses. Each form within treats the previous
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form as its subject, like a chain of `.` (dot) operators in C-like languages.
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in square brackets rather than parentheses. Each expression within acts upon the
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result of the previous one, like a chain of `.` (dot) operators in C-like
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languages.
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```common-lisp
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[foo bar baz quux]
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;; C++: foo.bar.baz.quux
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[foo (bar) (baz) (quux)]
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;; C++: foo.bar().baz().quux()
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```
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To access a slot, just put the slot name after the object:
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To call a method, just write it after the object:
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``` common-lisp
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[object slot-name]
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;; => (slot-value object 'slot-name)
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(setf [object slot-name] value)
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;; => (setf (slot-value object 'slot-name) value)
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[object (method args...)]
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;; => (method object args...)
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```
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`slot-name` doesn't have to be an unquoted symbol:
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Slot accessors, and other methods that don't take additional arguments, can be
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written without enclosing parentheses:
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``` common-lisp
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(defun choose-slot (x)
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(if (<= x 0) 'pos-slot 'neg-slot))
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(setf [object (choose-slot -1)] value)
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(defvar slot-var 'slot-name)
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(setf [object `,slot-var] value)
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```
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To call a method, write an S-expression as you normally would, but put a `.`
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(dot) before its name:
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``` common-lisp
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[object (.method arg-1 arg-2 ... arg-N)]
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;; => (method object arg-1 arg-2 ... arg-N)
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[object get-something]
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;; => (get-something object)
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```
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Under the hood, this just passes `object` as the first argument to `method`, so
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you can do stuff like this (I won't kinkshame you, but your coworkers might):
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```common-lisp
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[object slot-name (.setf value)]
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;; => [(slot-value object 'slot-name) (.setf value)]
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[object (slot-value 'slot-name) (setf value)]
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;; => [(slot-value object 'slot-name) (setf value)]
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;; => (setf (slot-value object 'slot-name) value)
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```
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And, of course, you can chain multiple slot accesses and method calls together:
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To access slots directly, use the `:slot` keyword:
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``` common-lisp
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[object child (.method-of-child) (.method-of-return-value) slot-of-return-value]
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;; => [(slot-value object 'child) (.method-of-child) ...]
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;; => [(method-of-child (slot-value object 'child)) (.method-of-return-value) ...]
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;; => [(method-of-return-value (method-of-child ...)) slot-of-return-value]
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;; => (slot-value (method-of-return-value ...) 'slot-of-return-value)
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```
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**NEW:** You can also call slot accessors without wrapping them in a cons. (This
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works for any method that takes no additional arguments, but that might cause
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code readability issues.)
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``` common-lisp
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[object .slot-accessor]
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;; => (slot-accessor object)
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[object :slot slot-name]
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;; => (slot-value object 'slot-name)
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```
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## License
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`objective-lisp` is public domain. You can do whatever you want with it. I don't
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really care about credit, it's just a silly little thing I wrote in a few hours.
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`objective-lisp` is public domain (CC0). You can do whatever you want with it. I
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don't really care about credit, it's just a silly little thing I wrote in a few
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hours. (And then rewrote just now because the syntax sucked.)
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But if you find it useful, *please* let me know. I'd love to hear about it.
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@ -3,8 +3,8 @@
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(defsystem "objective-lisp"
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:description "Syntactic sugar for object-oriented Lisp."
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:version "1.0"
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:version "2.0"
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:author "~keith"
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:homepage "https://bytes.keithhacks.cyou/keith/objective-lisp"
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:license "Public Domain"
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:license "Public Domain/CC0"
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:components ((:file "objective-lisp")))
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@ -3,94 +3,49 @@
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(defpackage objective-lisp
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(:use common-lisp)
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(:export +open-construct-char+ +close-construct-char+ +method-char+
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read-construct-contents
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destructure-construct
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read-method-name
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read-open-construct
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(:export +open-char+ +close-char+
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read-construct-item
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read-construct
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read-unexpected))
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(in-package objective-lisp)
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(defparameter +open-construct-char+ #\[)
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(defparameter +close-construct-char+ #\])
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(defparameter +method-char+ #\.)
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(defconstant +open-char+ #\[)
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(defconstant +close-char+ #\])
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;; DONE
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;; (setf (slot-value object 'slot) value)
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;; => (setf [object slot] value)
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(defun read-construct-item (sexpr stream)
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"Recursively read and rewrite an objective-lisp construct."
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(if (char= (peek-char t stream t nil t) +close-char+)
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; We've hit the end, return the sexpr we built
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(progn (read-char stream t nil t)
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sexpr)
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(let ((item (read stream t nil t)))
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(cond
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; Method call [object (method args...)]
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((consp item)
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(read-construct-item `(,(car item) ,sexpr ,@(cdr item))
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stream))
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; Slot access [object :slot slot-name]
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((eq item :slot)
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(read-construct-item `(slot-value ,sexpr ',(read stream t nil t))
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stream))
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; Consless method call [object method]
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((symbolp item)
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(read-construct-item `(,item ,sexpr)
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stream))
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; Something else
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(t (error "Unexpected item ~S" item))
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))))
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;; DONE
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;; (setf (slot-value (slot-value object 'slot-a) 'slot-b) value)
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;; => (setf [object slot-a slot-b] value)
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;; TODO
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;; (object-method object args...)
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;; => [object (.method args...)]
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(defun read-construct-contents (stream end-char)
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"Read the contents of an objective-lisp construct."
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(loop until (char= (peek-char t stream t nil t) end-char)
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collect (read stream t nil t)
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; Skip over end-char
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finally (read-char stream t nil t)))
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(defun quote-if-symbol (x)
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"Quote x if it's a symbol, return it verbatim otherwise."
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(if (symbolp x) `(quote ,x) x))
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(defun method-call-p (x)
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"Check if x is a sexpr of the form (.method args...)"
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(and (consp x) (consp (car x)) (eq (caar x) :method-call)))
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(defun consless-method-call-p (x)
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"Check if x is of the form .method (no arguments)"
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(and (consp x) (eq (car x) :method-call)))
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(defun destructure-construct (construct)
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"Recursively destructure an objective-lisp construct."
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(cond
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; Nothing left to destructure, return car
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((not (cdr construct))
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(car construct))
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; Method call [object (.method args...)]
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; => [object ((:method-call . method) args...)]
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((method-call-p (cadr construct))
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(let ((method-call (cadr construct)))
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(destructure-construct
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(cons `(,(cdar method-call) ,(car construct) ,@(cdr method-call))
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(cddr construct)))
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))
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; Consless method call [object .method]
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; => [object (:method-call . method)]
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((consless-method-call-p (cadr construct))
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(destructure-construct
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(cons `(,(cdadr construct) ,(car construct))
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(cddr construct)))
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)
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; Slot access [object slot]
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(t
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(destructure-construct
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(cons `(slot-value ,(car construct) ,(quote-if-symbol (cadr construct)))
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(cddr construct)))
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)))
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(defun read-method-name (stream char)
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"Read an objective-lisp method name."
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(declare (ignore char))
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(cons :method-call (read stream t nil t)))
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(defun read-open-construct (stream char)
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(defun read-construct (stream char)
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"Read an objective-lisp construct."
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(declare (ignore char))
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(let ((*readtable* (copy-readtable)))
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(set-macro-character +method-char+ 'read-method-name
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t) ; non-terminating so (12.34) doesn't become (12 (:method-call . 34))
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(destructure-construct (read-construct-contents stream +close-construct-char+))))
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(read-construct-item (read stream t nil t) ; 1st sexpr is the object, don't rewrite it
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stream))
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(defun read-unexpected (stream char)
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(declare (ignore stream))
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(error "Unexpected character ~S" char))
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(set-macro-character +open-construct-char+ 'read-open-construct)
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(set-macro-character +close-construct-char+ 'read-unexpected)
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(set-macro-character +open-char+ 'read-construct)
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(set-macro-character +close-char+ 'read-unexpected)
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