pascal/demo/demo_std.pas · 7354 字节 · 下载原文

{ demo_std.pas —— Pascal 第一层：**标准输入输出**（std）
  demo_std.pas -- Pascal layer 1: standard input/output (std)

  这一层只用 Pascal 自己的 `write` / `writeln`，不碰 Crt / Graph / 宿主 `ui_*` ——
  This layer uses only Pascal's own write / writeln and touches no Crt / Graph / host ui_* --
  所以它在任何后端上都是同一份行为，也是四份 demo 里唯一有"逐字节确定性输出"
  so it behaves identically on every backend, and it is the only one of the four demos with a byte-exact
  判据的一份（另外三份只能验"编得过、跑得完、不挂死"）。
  output check (the other three can only verify compile, run, no hang).

  跑法（桌面 vmlcli）：
  How to run (desktop vmlcli):
    dotnet scripts/vmlcli/bin/Release/net10.0/vmlcli.dll Examples/pascal/demo_std.pas

  期望输出（逐字节）：
  Expected output (byte exact):
    === Pascal 标准输出 demo ===
    === Pascal standard output demo ===
    字符串: 你好，世界
    string: hello, world
    整数: 42
    integer: 42
    计算: 7 * 6 = 42
    arithmetic: 7 * 6 = 42
    整除: 17 div 5 = 3
    integer division: 17 div 5 = 3
    取余: 17 mod 5 = 2
    remainder: 17 mod 5 = 2
    循环求和: 1..10 = 55
    loop sum: 1..10 = 55
    阶乘: 10! = 3628800
    factorial: 10! = 3628800
    字符宽度: length('abcd') = 4
    string length: length('abcd') = 4
    === done ===

  ◆ 两条本前端的写法要求（实测出来的，不是风格偏好）
  * Two coding rules for this frontend (measured, not a style preference)

    ① **`+` 不是字符串拼接**。`writeln('a' + 'b')` 打出的是 **195**
    1) + is not string concatenation. writeln('a' + 'b') prints 195
       —— 前端把两个字符串的**地址**当整数相加了。最小复现（两行的期望分别是
       -- the frontend adds the two string addresses as integers. Minimal repro (the two lines should print
       "ab" 与 "xyzw"）：
       "ab" and "xyzw" respectively):
         writeln('a' + 'b');            实际打出 195
         writeln('a' + 'b');            actually prints 195
         t := 'xy' + 'zw'; writeln(t);  实际打出空行
         t := 'xy' + 'zw'; writeln(t);  actually prints a blank line
       所以本文件里**一处字符串拼接都没有**：要拼就把几个值分别写进同一个
       So this file contains no string concatenation at all: to join values, pass them as separate
       `writeln` 实参表（`writeln('a', b, 'c')` 那条路是好的）。
       arguments of one writeln (the writeln('a', b, 'c') path works fine).

    ⚠ 写本文件时的一个小坑记在这儿：**Pascal 的花括号注释不嵌套** ——
    WARNING: one small trap found while writing this file: Pascal brace comments do not nest --
      本段散文里若出现一个左花括号再出现一个右花括号，**那个右花括号会提前
      if this prose contained an opening brace followed by a closing brace, that closing brace would
      收掉整段注释**，后面的散文全被当成代码（实测报「未知字符: ：」）。
      end the whole comment early and the rest of the prose would be parsed as code (it reports an unknown character).
      所以下面提到花括号一律用文字说，不写真符号。
      So below, braces are always named in words and never written literally.

    ② `Str(42, s)`（标准 Pascal 的整数转串）**本前端没有** —— 走到「未定义的函数
    2) Str(42, s) (standard Pascal int to string) does not exist in this frontend -- it ends up at undefined function
       'Str'」。要在绘图窗口里显示数字得自己写整转串（本目录的 `demo_ui.pas`
       Str. To show numbers in a draw window you must write your own int-to-string (demo_ui.pas in this directory
       干脆不显示数字，用形状与固定标签表达状态，与 `sokoban.f90` 同一取舍）。
       simply shows no numbers, using shapes and fixed labels for state, the same trade-off as sokoban.f90).
}

program DemoStd;

{ `ui_scr_get_language()` 来自宿主 UI 库 —— 声明在 `Lib/pascal/vml_ui.pas`。
  ui_scr_get_language() comes from the host UI library declared in Lib/pascal/vml_ui.pas.
  ⚠ 零参函数**裸写**（`ui_scr_get_language` 不带括号）时，只有 `interface` 段里声明过
  WARNING: when a zero-arg function is written bare (no parentheses), only a declaration
  才认得出这是一次调用而不是变量 —— 而 Pascal 里这种裸写很常见，所以这条 `uses` 留着。
  in the interface section marks it as a call rather than a variable, so this `uses` stays.
  （本文件恰好写的是带括号的 `ui_scr_get_language()` —— 那种写法删掉 `uses` 也编得过；
  (this file happens to use the parenthesised form, which compiles even without `uses`;
  但**改一个字**变成裸写就会报「未声明的变量」，所以别删它。）
  but a one-character edit to the bare form would report an undeclared variable, so keep it.) }
uses vml_ui;

var
  i, sum, fact, lang: integer;

begin
  { 界面语言：0 = 中文 / 1 = 英文（ui_scr_get_language 是 syscall，开局查一次） }
  { UI language: 0 = Chinese / 1 = English (ui_scr_get_language is a syscall, queried once at startup) }
  lang := ui_scr_get_language();
  if lang = 0 then writeln('=== Pascal 标准输出 demo ===') else writeln('=== Pascal standard output demo ===');

  { ① 字符串字面量（含中文 —— 源码按 UTF-8 存，词法器直通） }
  { 1) string literals (including Chinese -- the source is stored as UTF-8 and the lexer passes it through) }
  if lang = 0 then writeln('字符串: 你好，世界') else writeln('string: hello, world');

  { ② 整数 }
  { 2) integer }
  if lang = 0 then writeln('整数: ', 42) else writeln('integer: ', 42);

  { ③ 整数运算 }
  { 3) integer arithmetic }
  if lang = 0 then writeln('计算: 7 * 6 = ', 7 * 6) else writeln('arithmetic: 7 * 6 = ', 7 * 6);

  { ④ 整除与取余：Pascal 用 `div` / `mod`（不是 `\` / `%`） }
  { 4) integer division and remainder: Pascal uses div / mod (not backslash / percent) }
  if lang = 0 then writeln('整除: 17 div 5 = ', 17 div 5) else writeln('integer division: 17 div 5 = ', 17 div 5);
  if lang = 0 then writeln('取余: 17 mod 5 = ', 17 mod 5) else writeln('remainder: 17 mod 5 = ', 17 mod 5);

  { ⑤ 循环求和 1..10 }
  { 5) loop sum 1..10 }
  sum := 0;
  for i := 1 to 10 do
    sum := sum + i;
  if lang = 0 then writeln('循环求和: 1..10 = ', sum) else writeln('loop sum: 1..10 = ', sum);

  { ⑥ 循环求阶乘 10! }
  { 6) loop factorial 10! }
  fact := 1;
  for i := 1 to 10 do
    fact := fact * i;
  if lang = 0 then writeln('阶乘: 10! = ', fact) else writeln('factorial: 10! = ', fact);

  { ⑦ 字符串长度（`length` 是语言内建的，走的是 VML 字符串体系） }
  { 7) string length (length is built into the language and goes through the VML string system) }
  if lang = 0 then writeln('字符宽度: length(''abcd'') = ', length('abcd')) else writeln('string length: length(''abcd'') = ', length('abcd'));

  writeln('=== done ===');
end.