将字符串公式解析为整数结果 [英] Parsing a string formula to an integer result
问题描述
我正在做一些解析工作,太复杂,无法进入细节,但有一件简单的事情我需要做(至少简单的概念,也许不是简单的答案)。我可能有一个字符串中的公式,如下面的示例。我需要一个功能,使用一个格式不正确的公式字符串,解析出来并计算结果。
示例:
(10/2)+(10/30)
5+(10/30)
5 + 3
8
或:
(12.5 - (0.5 * 5))/ 2
(12.5 - 2.5)/ 2
10/2
5
规则:
- 空格将被忽略
- PEMDAS方法必须完全适用
- 结果应始终一个四舍五入的整数
- 没有变量将存在,已经转换为数字
- 十进制数字可能是输入的一部分
现在的解析我已经在工作,只是得到这些公式字符串中的一个 - 但从那里,我不知道如何执行实际的计算。我正在做的是做一些划线的划线笔画画布,这里有一些示例脚本:
Var W 50
Var H 50
笔风格清除
笔颜色$ 000000
笔宽度3
画笔样式固体
画笔颜色{FORM_COLOR}
Rect 0 0 {WIDTH} {HEIGHT}
画笔颜色$ 501010
椭圆@W @H 450 450
画笔颜色$ 602020
椭圆100 100 400 400
画笔颜色$ 703030
椭圆形150 150 350 350
刷子颜色$ 804040
椭圆形200 200 300 300
EllipseG 200 200 300 300 6 2
笔式固体
笔宽2
笔颜色{FONT_COLOR}
MoveTo 0 0
LineTo 500 500
MoveTo 0 500
LineTo 500 0
所有这些都已经有效了,但现在我想说...例如...
code> Var W
Var H
设置W 50
设置H 50
画笔颜色$ 602020
椭圆(@W,@H,500 - @W ,500 - @H
设置W 100
设置H 100
画笔颜色$ 703030
Ell ipse(@W,@H,500 - @W,500 - @H
设置W 150
设置H 150
画笔颜色$ 804040
椭圆(@W,@H, 500 - @W,500 - @H
所以 500 - @W
我已将其转换为 500 - 50
,但现在我需要发送字符串 500 - 50
进入此功能以获得结果 450
。
编辑:解决 / p>
我按照推荐使用 parser10
,它完美适用于我需要做的工作。以下是我的脚本代码示例代码:
Var S 4
Var D @S
Var L 0
Var T 0
Var R {WIDTH}
Var B {HEIGHT}
笔风格清除
笔颜色$ 00000000
笔宽3
画笔风格固体
画笔颜色{FORM_COLOR}
矩形0 0 {宽度} {HEIGHT}
设置D @ D + @ S
画笔颜色$ 00400000
Ellipse @ L + @ D @ T + @ D @R - (@ D * 2)@B - (@ D * 2)
设置D @ D + @ S
画笔颜色$ 00501010
椭圆@ L + @ D @ T + @ D @R - (@ D * 2)@B - (@ D * 2)
设置D @ D + @ S
画笔颜色$ 00602020
椭圆@ L + @D @ T + @ D @R - (@ D * 2)@B - (@ D * 2)
设置D @ D + @ S
画笔颜色$ 00703030
椭圆@ L + @ D @ T + @ D @R - (@ D * 2)@B - (@ D * 2)
设置D @ D + @ S
画笔颜色$ 00804040
椭圆@ L + @ D @ T + @D @R - (@ D * 2)@B - (@ D * 2)
设置D @ D + @ S
画笔颜色$ 00905050
椭圆@ L + @ D @ T + @ D @R - (@ D * 2)@B - (@ D * 2)
设置D @ D + @ S
画笔颜色$ 00FB6060
椭圆@ L + @ D @ T + @ D @ R - (@ D * 2)@B - (@ D * 2)
@是一个变量,我使用 StringReplace()
根据 Var
部分中声明的内容进行转换。
Parser10 ,最初由Renate Schaaf为Delphi 1编写,后来由Alin Flaider和Stefan Hoffmeister升级到Delphi2和3,这是一个相当简单的数学解析器。它将为简单的表达做好工作,可以作为更复杂工作的样板。
它不是为了速度而建。
更新:
Hallvard Vassbotn更新了Parser10,并添加了一些文档。从此处载入。
I'm doing some parsing work, too complex to get into details, but there's one simple thing I need to do (at least simple concept, maybe not simple answer). I might have a formula in a string such as the samples below. I need a function that will take a loosly-formatted formula string, parse it out, and calculate the result.
Sample:
(10 / 2)+(10/30)
5+(10/30)
5+3
8
Or:
(12.5 - (0.5 * 5)) / 2
(12.5 - 2.5) / 2
10 / 2
5
Rules:
- Spaces are to be ignored
- PEMDAS method must entirely apply
- Result shall be always a rounded Integer
- No variables will exist, already converted to numbers
- Decimal numbers might be part of the input
The existing parsing I already have working just gets one of these formula strings - but from there, I have no clue how to perform the actual calculations. What I'm doing specifically is doing a little line deliminated scripter to draw to a canvas, here's some sample script:
Var W 50
Var H 50
Pen Style Clear
Pen Color $000000
Pen Width 3
Brush Style Solid
Brush Color {FORM_COLOR}
Rect 0 0 {WIDTH} {HEIGHT}
Brush Color $501010
Ellipse @W @H 450 450
Brush Color $602020
Ellipse 100 100 400 400
Brush Color $703030
Ellipse 150 150 350 350
Brush Color $804040
Ellipse 200 200 300 300
EllipseG 200 200 300 300 6 2
Pen Style Solid
Pen Width 2
Pen Color {FONT_COLOR}
MoveTo 0 0
LineTo 500 500
MoveTo 0 500
LineTo 500 0
All that already works, but now I want to say for example...
Var W
Var H
Set W 50
Set H 50
Brush Color $602020
Ellipse(@W, @H, 500 - @W, 500 - @H
Set W 100
Set H 100
Brush Color $703030
Ellipse(@W, @H, 500 - @W, 500 - @H
Set W 150
Set H 150
Brush Color $804040
Ellipse(@W, @H, 500 - @W, 500 - @H
So the 500 - @W
I already convert it to 500 - 50
but now I need to send the string 500 - 50
into this function to get the result 450
.
EDIT: Solved
I'm using the parser10
as recommended, and it works perfectly for what I need to do. Here's a sample snippet of my script code:
Var S 4
Var D @S
Var L 0
Var T 0
Var R {WIDTH}
Var B {HEIGHT}
Pen Style Clear
Pen Color $00000000
Pen Width 3
Brush Style Solid
Brush Color {FORM_COLOR}
Rect 0 0 {WIDTH} {HEIGHT}
Set D @D+@S
Brush Color $00400000
Ellipse @L+@D @T+@D @R-(@D*2) @B-(@D*2)
Set D @D+@S
Brush Color $00501010
Ellipse @L+@D @T+@D @R-(@D*2) @B-(@D*2)
Set D @D+@S
Brush Color $00602020
Ellipse @L+@D @T+@D @R-(@D*2) @B-(@D*2)
Set D @D+@S
Brush Color $00703030
Ellipse @L+@D @T+@D @R-(@D*2) @B-(@D*2)
Set D @D+@S
Brush Color $00804040
Ellipse @L+@D @T+@D @R-(@D*2) @B-(@D*2)
Set D @D+@S
Brush Color $00905050
Ellipse @L+@D @T+@D @R-(@D*2) @B-(@D*2)
Set D @D+@S
Brush Color $00FB6060
Ellipse @L+@D @T+@D @R-(@D*2) @B-(@D*2)
Anything starting with an @ is a variable, which I do a StringReplace()
to convert all those based on what was declared in the Var
section.
Parser10, written originally by Renate Schaaf for Delphi 1 and later upgraded to Delphi2 and 3 by Alin Flaider and Stefan Hoffmeister, is a fairly simple math parser. It will do the job for simple expressions and can serve as a boilerplate for more complex work.
It is not built for speed though.
Update :
Hallvard Vassbotn made an update of Parser10 and added some documentation. Load it from here.
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