［创建时间］：<2018-05-29 Tue 07:50:42 UTC+08:00>
［更新时间］：<2018-05-29 Tue 13:50:44 UTC+08:00>
总结使用Common Lisp包ParenScript的实践过程。
使用Quicklisp提前加载程序，再编写ParenScript语句，用于根据当前的时间来判断是白天还是黑夜：
(ql:quickload :parenscript)
(in-package :parenscript)
(ps (if (>= (new (chain (-date) (get-hours)))
20)
"evening"
"day"))
ParenScript语句的目的是生成下列JavaScript语句：
if (new Date().getHours() >= 20) {
'evening';
} else {
'day';
};
复制到浏览器的终端、NodeJS等任意能执行JavaScript语句的程序里执行，将得到：
'day'
先展开ParenScript程序为JavaScript程序，再执行JavaScript程序。
需要提前准备好：
过程：
编写纯粹的ParenScript代码
(if (>= (new (chain (-date) (get-hours)))
20)
"evening"
"day")
与浏览器建立联系
M-x run-skewer
像SLIME一样求值上述ParenScript代码
M-x trident-eval-last-expression
"day"
需要提前准备好：
过程：
编写纯粹的ParenScript代码
(if (>= (new (chain (-date) (get-hours)))
20)
"evening"
"day")
与NodeJS建立联系
(defun trident-nodejs-start ()
(interactive)
(unless (js-comint-get-process)
(js-comint-start-or-switch-to-repl)))
(defun trident-nodejs--eval (string)
(unless (js-comint-get-process)
(error "Please use `M-x trident-nodejs-start' to start NodeJS first."))
(trident-with-expansion (code string)
(js-comint-send-string code))
(js-comint-start-or-switch-to-repl))
(defun trident-nodejs-eval-last-expression ()
"参考`trident-eval-last-expression'"
(interactive)
(trident-nodejs--eval
(slime-last-expression)))
(defun trident-nodejs-eval-defun ()
(interactive)
(trident-nodejs--eval
(slime-defun-at-point)))
(defun trident-nodejs-eval-region (beg end)
(interactive "r")
(trident-nodejs--eval
(buffer-substring-no-properties beg end)))
(defun trident-nodejs-eval-buffer ()
(interactive)
(trident-nodejs-eval-region (point-min)
(point-max)))
像SLIME一样求值上述ParenScript代码
M-x trident-nodejs-eval-last-expression
'day'
定义Common Lisp包的命名空间是＂day-or-evening＂：
(ql:quickload :parenscript)
(in-package :common-lisp)
(defpackage #:day-or-evening
(:use #:common-lisp))
(setf (parenscript:ps-package-prefix :day-or-evening)
"DOE$")
展开后JavaScript包的前缀名是＂DOE$＂。
譬如下列ParenScript代码：
(in-package #:common-lisp)
(defun day-or-evening::day-or-evening ()
(if (>= (parenscript:new
(parenscript:chain (-date)
(get-hours)))
20)
"evening"
"day"))
或：
(in-package #:day-or-evening)
(defun day-or-evening ()
(if (>= (parenscript:new
(parenscript:chain (#:-date)
(#:get-hours)))
20)
"evening"
"day"))
将展开成：
function DOE$dayOrEvening() {
return new Date().getHours() >= 20 ? 'evening' : 'day';
};
在上述ParenScript代码里，要么在＂common-lisp＂命名空间里，要么在＂day-or-evening＂命名空间里定义函数。
在两个不同的命名空间里定义函数时，使用ParenScript函数、JavaScript函数时都需要带上长长的前缀，这不免麻烦。
我采用的做法是分而治之。
只要是JavaScript函数就在＂common-lisp＂的命名空间里提前定义，带上长长的＂day-or-evening＂前缀，此为筑基。
譬如，提前定义喜闻乐见的JavaScript方法＂getElementById＂：
(in-package #:common-lisp)
(defun day-or-evening::get-element-by-id (id)
"getElementById"
(document.get-element-by-id id))
展开式为：
function DOE$getElementById(id) {
return document.getElementById(id);
};
在这个基础上，在＂day-or-evening＂的命令空间里，随意地使用JavaScript函数，就像这些函数是Common Lisp的内部函数一样，此时前缀可免，补全可用，文档可用，JavaScript与Common Lisp合二为一。
譬如，上述定义的＂get-element-by-id＂函数：
(in-package #:day-or-evening)
(get-element-by-id "element-id")
展开式为：
DOE$getElementById('element-id');
当这些JavaScript函数过于频繁地在多个程序里出现时，可以分离出所有的提前定义过程，创建一个新的包，姑且唤作＂lscript＂，只要是ParenScript程序：
(let ((list '()))
(dolist (i '(1 2))
(push i list)))
展开式为：
(function () {
var list = [];
for (var i = null, _js_arrvar19 = [1, 2], _js_idx18 = 0; _js_idx18 < _js_arrvar19.length; _js_idx18 += 1) {
i = _js_arrvar19[_js_idx18];
push(i, list);
};
})();
上述＂_js_＂前缀的随机名称，本来是为了消除名称的冲突，但无疑增加了版本管理的因难，不能直接去除，又非用不可，着实麻烦。
姑且有两步来缓解无用的版本更新问题。
可以在生成JavaScript文件之前，检测git仓库里的ParenScript文件是否发生了变化，在没有任何变化时，会得到＂nothing to commit, working tree clean＂，否则，将ParenScript文件转换为JavaScript文件。
也可以使用预先定义的函数来替换能产生随机名称的函数，让＂_js_＂前缀的随机名称只出现在一个位置。
譬如对于上述＂dolist＂过程，创建＂cl-mapc＂函数：
(defun cl-mapc (f-function list)
(let ((l-list '()))
(dolist (i list)
(funcall f-function
i l-list))))
展开式：
function clMapc(fFunction, list) {
var lList = [];
for (var i = null, _js_idx23 = 0; _js_idx23 < list.length; _js_idx23 += 1) {
i = list[_js_idx23];
fFunction(i, lList);
};
};
而后，只要是类似的过程，直接使用＂cl-mapc＂函数而不是＂dolist＂：
(cl-mapc (function push)
'(1 2))
展开式：
clMapc(push, [1, 2]);
引用项目
在网页应用里引用＂day-or-evening.js＂
<script src='day-or-evening.js'></script>
在asdf里依赖项目＂day-or-evening＂
(asdf:defsystem #:foo
:depends-on (#:day-or-evening))
使用外部操作符
(day-or-evening:day-or-evening)
DOE$dayOrEvening();
'day'
(asdf:defsystem #:day-or-evening
:depends-on (#:cl-who
#:parenscript
#:cl-css
#:external-program)
:serial t
:components ((:file "package")
(:file "utility")
(:file "html")
(:file "css")
(:file "js")
(:file "build")))
(in-package #:common-lisp)
(defpackage #:day-or-evening
(:use #:common-lisp)
(:export #:get-hours
#:day-or-evening))
(setf (ps:ps-package-prefix :day-or-evening)
"DOE$")
(in-package #:day-or-evening)
字符串导出为文件
(defun string-to-file (string destination-file)
(with-open-file (out destination-file
:direction :output
:if-exists :supersede)
(princ string out)))
git仓库里文件没有更新
(defun nothing-to-commit-p (filespec)
(let ((old (sb-posix:getcwd))
(new (make-pathname :directory (pathname-directory filespec)))
(filename (concatenate 'string
(pathname-name filespec)
"."
(pathname-type filespec))))
(cl-ppcre:scan-to-strings "nothing to commit, working tree clean"
(with-output-to-string (out)
(sb-posix:chdir new)
(let ((result (external-program:run "git"
`("status" ,filename)
:output out)))
(sb-posix:chdir old)
result)))))
给生成的HTML、CSS、JavaScript文件带上版权声明
(defvar *license*
"Copyright (c) 2018, SunDawning <[email protected]> https://github.com/SunDawning
All rights reserved.")
(defun string-to-html-file (string destination-file)
(string-to-file (format nil "~A~%" string *license*)
destination-file))
(defun string-to-css-file (string destination-file)
(string-to-file (format nil "~A~%/*~%~A~%*/" string *license*)
destination-file))
(defun lisp-file-to-js-file (source-file destination-file &key do-not-use-strict-p force-export-p)
"JavaScript语法支持严格模式：”use strict” - daoyuly - 博客园: http://www.cnblogs.com/daoyuly/archive/2013/03/26/2983614.html"
(if (or force-export-p
(not
(probe-file destination-file)))
(with-open-file (out destination-file
:direction :output
:if-exists :supersede)
(unless do-not-use-strict-p
(format out "~S;~%"
"use strict"))
(princ (parenscript:ps-compile-file source-file)
out)
(format out "/*~%~A~%*/"
*license*))
(unless (nothing-to-commit-p source-file)
(lisp-file-to-js-file source-file destination-file :force-export-p t))))
(in-package #:day-or-evening)
(defparameter *html*
(cl-who:with-html-output-to-string (*standard-output* nil :prologue t
:indent t)
(:html
(:head
(:meta :http-equiv "Content-Type"
:content "text/html,charset=utf-8")
(:meta :http-equiv "Content-Type"
:name "viewport"
:content "width=device-width")
(:title "Day or Evening")
(:base :target "_blank")
(:link :type "text/css"
:rel "stylesheet"
:href "day-or-evening.css"))
(:body
(:script :src "day-or-evening.js")))))
(in-package #:day-or-evening)
(defparameter *css*
(cl-css:css
`(("body"
:background "black"
:font-size "16px"))))
JavaScript
(in-package #:common-lisp)
(defun day-or-evening::get-hours ()
(parenscript:new
(parenscript:chain (-date)
(get-hours))))
Common Lisp
(in-package #:day-or-evening)
(defun day-or-evening ()
(if (>= (get-hours)
20)
"evening"
"day"))
(in-package #:day-or-evening)
(let ((directory (asdf:system-source-directory :day-or-evening)))
(lisp-file-to-js-file (merge-pathnames "js.lisp" directory)
(merge-pathnames "day-or-evening.js" directory))
(string-to-html-file *html*
(merge-pathnames "day-or-evening.html" directory))
(string-to-css-file *css*
(merge-pathnames "day-or-evening.css" directory)))
有了＂build.lisp＂文件后，只要：
(ql:quickload :day-or-evening)
就能生成JavaScript文件、HTML文件、CSS文件，完成项目搭建、更新、维护过程。
