马上要期末考试了，很多长方体计算题，5分钟写了个长方体表面积以及体积计算小工具，先看效果

输入长宽高，马上出结果

然后看下我们的需求分析

了解当前的计算公式。

设计输入输出

方案设计：

代码编写：

测试：

一气呵成，用时5分钟

代码如下

form代码

object Form5: TForm5

Left = 715

Top = 312

Caption = #38271#26041#20307#34920#38754#31215#19982#20307#31215#35745#31639#24037#20855

ClientHeight = 538

ClientWidth = 666

Color = clBtnFace

Font.Charset = DEFAULT_CHARSET

Font.Color = clWindowText

Font.Height = -12

Font.Name = 'Segoe UI'

Font.Style = []

Position = poDesigned

TextHeight = 15

object btn1: TBitBtn

Left = 533

Top = 55

Width = 75

Height = 25

Caption = #35745#31639

TabOrder = 0

OnClick = btn1Click

end

object lbledt1: TLabeledEdit

Left = 48

Top = 57

Width = 121

Height = 23

EditLabel.Width = 13

EditLabel.Height = 15

EditLabel.Caption = #38271

TabOrder = 1

Text = ''

TextHint = #36755#20837#38271#24230

end

object lbledt2: TLabeledEdit

Left = 210

Top = 57

Width = 121

Height = 23

EditLabel.Width = 13

EditLabel.Height = 15

EditLabel.Caption = #23485

TabOrder = 2

Text = ''

TextHint = #36755#20837#23485#24230

end

object lbledt3: TLabeledEdit

Left = 371

Top = 57

Width = 121

Height = 23

EditLabel.Width = 13

EditLabel.Height = 15

EditLabel.Caption = #39640

TabOrder = 3

Text = ''

TextHint = #36755#20837#39640#24230

end

object Memo1: TMemo

Left = 0

Top = 200

Width = 666

Height = 338

Align = alBottom

TabOrder = 4

end

object btn2: TBitBtn

Left = 533

Top = 144

Width = 75

Height = 25

Caption = #25302#24335#35745#31639

TabOrder = 5

OnClick = btn2Click

end

object lbledt4: TLabeledEdit

Left = 40

Top = 145

Width = 449

Height = 23

EditLabel.Width = 26

EditLabel.Height = 15

EditLabel.Caption = #24335#23376

TabOrder = 6

Text = ''

TextHint = #36755#20837#35745#31639#24335#23376#25903#25345#21152#20943#20056#38500#28151#21512#36816#31639'96+52+4+8'

OnChange = lbledt4Change

end

end

程序代码

unit Unit5;

interface

uses

Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,

Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.Mask, Vcl.ExtCtrls, expclass,

Vcl.Buttons;

type

TForm5 = class(TForm)

btn1: TBitBtn;

lbledt1: TLabeledEdit;

lbledt2: TLabeledEdit;

lbledt3: TLabeledEdit;

Memo1: TMemo;

btn2: TBitBtn;

lbledt4: TLabeledEdit;

procedure btn1Click(Sender: TObject);

procedure btn2Click(Sender: TObject);

procedure lbledt4Change(Sender: TObject);

private

{ Private declarations }

public

{ Public declarations }

end;

var

Form5: TForm5;

implementation

{$R *.dfm}

procedure TForm5.btn1Click(Sender: TObject);

var

nl,nw,nh:Double;

nbmj,nvol:Double;

begin

nl:=StrToFloatDef(lbledt1.Text,0);

nw:=StrToFloatDef(lbledt2.Text,0);

nH:=StrToFloatDef(lbledt3.Text,0);

nbmj:=(NL*NW+NL*NH+NW*NH)*2;

nvol:=NL*NW*NH;

Memo1.Lines.Add(format('长=%.2f,宽=%.2f 高：%.2f 表面积 ：%.2f，体积：%.2f',[nl,NW,NH,nbmj,NVOL]));

end;

procedure TForm5.btn2Click(Sender: TObject);

var

ss:TExpression;

ns:Extended;

begin

try

ss:=TExpression.Create((lbledt4.Text));

ns:=ss.Calc;

if ss.oResok then

Memo1.Lines.Add(Format('%s=%.2f',[lbledt4.Text,ns]))

else

Memo1.Lines.Add(Format('%s 格式不正确',[lbledt4.Text]));

btn2.Enabled:=False;

except

on e:Exception do

Memo1.Lines.Add(e.Message);

end;

end;

procedure TForm5.lbledt4Change(Sender: TObject);

begin

btn2.Enabled:=True;

end;

end.

unit expclass;

interface

uses

SysUtils, Math;

const

CALCERR = -999999999999.99;

type

TExpression = class //表达式 类

private

CurPos: integer; //字符位置

MaxPos: integer; //最大

iExp: string; //输出信息

token: string; //记号

dataList: array of Double;

sz: Double;

function IsDigit(ch: char): boolean; //是不是数字

function IsLetter(ch: char): boolean; //是不是字母

function CheckExp: boolean; // 首先对表达式进行检查

function gettoken: integer; //获取记号

function term: extended; //分组

function factor: extended; //因数

public

oResok: boolean;

constructor Create(AExpression: string);

function Calc: extended;

end;

const

ID = 1; // var

NUM = 2; // numbers

PLUS = 3; // '+'

MINUS = 4; // '-'

TIMERS = 5; // '*'

OVER = 6; // '/'

LPAREN = 7; // '('

RPAREN = 8; // ')'

POWers = 9; // '^'

ERROR = 255; // Errors

OPS = '+-*/()^'; // Oprators 优先级

implementation

function TExpression.IsLetter(ch: Char): boolean;

begin

if (ch in ['a'..'z']) or (ch in ['A'..'Z']) then

result := true

else

result := false;

end;

function TExpression.IsDigit(ch: Char): boolean;

begin

if (ch in ['0'..'9']) or (ch = '.') then

result := True

else

Result := False;

end;

// Get Token and Token Type from curPos

function TExpression.gettoken: integer;

var

Skip: boolean;

begin

result := ERROR; //错误优先级最高 255

Skip := False; // 指示是否忽略指针移动

token := ''; //标记值为 空 ""

while (CurPos <= MaxPos) and (iExp[CurPos] = ' ') do //当前光标小于最大位数 并且 空格 增加一位

inc(CurPos);

// 加入对负号的处理：如果前次token为 '('，或第一个符号就是'-'，则减号是负号

if Pos(iExp[CurPos], OPS) > 0 then //运算符处理

begin

case iExp[CurPos] of

'+': result := PLUS;

'-':

begin

if (CurPos > 1) and (iExp[CurPos - 1] <> '(') then

result := MINUS

else

begin

token := '-';

inc(CurPos);

while (CurPos <= MaxPos) and IsDigit(iExp[CurPos]) do

begin

token := token + iExp[CurPos];

sz := StrToFloat(token);

inc(CurPos);

end;

Skip := True;

result := NUM;

end;

end;

'*': result := TIMERS;

'/': result := OVER;

'(': result := LPAREN;

')': result := RPAREN;

'^': result := POWERs;

end;

if not Skip then

inc(CurPos);

end

else

begin

if IsLetter(iExp[CurPos]) then //维持在字母状态

begin

while (CurPos <= MaxPos) and (IsLetter(iExp[CurPos]) or

IsDigit(iExp[CurPos])) do

begin

token := token + iExp[CurPos];

inc(CurPos);

end;

result := ID;

end

else if IsDigit(iExp[CurPos]) then //维持在数字状态

begin

while (CurPos <= MaxPos) and IsDigit(iExp[CurPos]) do

begin

token := token + iExp[CurPos]; // token=2 tcken=5

inc(CurPos);

end;

result := NUM;

end;

end;

if result = ERROR then

oResok := false;

end;

function TExpression.term: extended; //首次计算

var

temp: extended;

begin

result := factor(); // 拆解

while (CurPos <= MaxPos) and ((iExp[CurPos] = '*') or (iExp[CurPos] = '/') or

(iExp[CurPos] = '^'))

do // 乘除号 优先

begin

case gettoken() of

POWers: Result := Power(Result, factor);

TIMERS:

result := result * factor();

OVER:

begin

temp := factor;

if temp <> 0 then

result := result / temp

else

begin

oResok := false;

result := 0;

end;

end;

end;

end;

end;

function TExpression.factor(): extended;

begin

result := 0.0; //等于0？

case gettoken() of //获取元素标记

NUM:

begin

result := StrtoFloatDef(token, 0); //数字1 ,2

sz := result;

end;

LPAREN: //左括号

begin

result := calc;

if gettoken() <> RPAREN then

begin

oResok := false;

result := 0;

end;

end;

POWers:

begin

result := Power(sz, factor);

end;

ID:

begin

if token = 'cos' then

begin

Result := factor();

Result := Cos(Result);

end

else if token = 'sin' then

begin

Result := factor();

Result := Sin(Result);

end

else if token = 'tan' then

begin

Result := factor();

Result := Tan(Result);

end

else if token = 'cot' then

begin

Result := factor();

Result := Cotan(Result);

end

else if token = 'ln' then

begin

Result := factor();

Result := Ln(Result);

end

else if token = 'e' then

begin

Result := 2.718281828459;

// Result := Ln(Result);

end

else if token = 'pi' then

begin

Result := 3.1415926535898;

end

else

Result := ERROR;

end;

end;

end;

function TExpression.CheckExp: boolean;

begin

Result:=Length( Trim(iExp))>0;

// result := true;

end;

constructor TExpression.Create(AExpression: string);

begin

iExp := LowerCase(AExpression);

CurPos := 1;

MaxPos := Length(iExp);

oResok := CheckExp;

end;

function TExpression.Calc: extended; //类函数

begin

if oResok then

begin

result := term(); //优先计算乘除

while (CurPos <= MaxPos) and ((iExp[CurPos] = '+') or (iExp[CurPos] = '-'))

do

//加减号其次 ，获取加号

begin

case gettoken() of

PLUS:

result := result + term();

MINUS:

result := result - term();

end;

end;

end

else

result := 0;

end;

end.