Scheme的GUI编程风格

chicken scheme Iup 教程链接：

在C语言里面，这样来显示一个对话框和按钮：

hello1.c
#include 
#include 

int exit_cb (void) {
  return IUP_CLOSE;
}

int main (int argc, char *argv[]) {

  // declare widgets
  Ihandle *btn, *lbl, *vb, *dlg;

  // initialize iup
  IupOpen(&argc, &argv);
  
  // create widgets and set their attributes
  btn=IupButton("&Ok", "");
  IupSetCallback(btn,"ACTION", (Icallback) exit_cb);
  IupSetAttribute(btn, "EXPAND", "Yes");
  IupSetAttribute(btn, "TIP", "Exit button");
  
  lbl=IupLabel("Hello,world!");

  vb=IupVbox(lbl, btn, NULL);
  IupSetAttribute(vb, "GAP", "10");
  IupSetAttribute(vb, "MARGIN", "10x10");
  IupSetAttribute(vb, "ALIGNMENT", "ACENTER");

  dlg=IupDialog(vb);
  IupSetAttribute(dlg, "TITLE", "Hello");

  // Map widgets and show dialog
  IupShow(dlg);

  // Wait for user interaction
  IupMainLoop();

  // Clean up
  IupDestroy(dlg);
  IupClose();
  return EXIT_SUCCESS;
}

可以看到，在C语言里面是标准的命令式语言风格。

Chicken-scheme里面，可以这样写：

(use iup)

(define (cb-exit self) 'close)

(define btn (button))
(set! (callback btn action:) cb-exit)
(set! (attribute btn title:) '&Ok)
(set! (attribute btn expand:) 'Yes)
(set! (attribute btn tip:) "Close button")

(define lbl (label "Hello World!")) 

(define vb (vbox lbl btn))
(attribute-set! vb gap: 10)
(attribute-set! vb margin: '15x15)
(attribute-set! vb alignment: 'ACENTER)

(define dlg (dialog vb))
(attribute-set! dlg title: 'Hello)

(show dlg)
(main-loop)
(destroy! dlg)
(exit 0)

还是命令式风格。

看下面的写法：

(use iup)

(define dlg
  (dialog
    (vbox
      (label "Hello, World!")
      (button title: '&Ok
              expand: 'Yes
              tip: "Close button"
              action: (lambda (self) 'close))
      gap: 10
      alignment: 'ACENTER
      margin: '15x15)
    title: 'IUP))

(show dlg)
(main-loop)
(destroy! dlg)
(exit 0)

里面定义对话框一段，是标准的函数式语言风格了。

看来GUI程序用函数式语言来写显得很精简，也很nature.

另注：

在具体实现的时候，是否会碰到求值顺序的问题？dialog和button会有定义顺序先后的问题吗？