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GeneralRe: Retrieve HWND of a control that has focus Pin
Richard MacCutchan11-Aug-18 21:56
protectorRichard MacCutchan11-Aug-18 21:56 
GeneralRe: Retrieve HWND of a control that has focus Pin
_Flaviu13-Aug-18 0:09
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GeneralRe: Retrieve HWND of a control that has focus Pin
Randor 13-Aug-18 1:51
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GeneralRe: Retrieve HWND of a control that has focus Pin
leon de boer12-Aug-18 3:47
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QuestionWhat is the magic incantation to select a row in a CListCtrl in report mode ? Pin
Maximilien9-Aug-18 9:09
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GeneralRe: What is the magic incantation to select a row in a CListCtrl in report mode ? Pin
David Crow9-Aug-18 9:47
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GeneralRe: What is the magic incantation to select a row in a CListCtrl in report mode ? Pin
Maximilien9-Aug-18 12:06
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Questionhow to use recursive descent algorithm to compute an arithmetical expression? Pin
tony_ming8-Aug-18 20:42
membertony_ming8-Aug-18 20:42 
I want to use recursive descent algorithm to compute an arithmetical expression, but I can't get the right value,so please tell me how to write the code
here is my grammar
E→E+T|E-T|T
T→T*F| T/F|F
F→(E)|i


the following is my code
<pre>
#include<stdio.h>    
#include<string> 
 using namespace std;
 int pos = 0;
 string str = "1+2*3-4";
 double E();
 double T();
 double F();

int main() {
	double v = E();
	printf("%f", v);
	getchar();
	return 0;
}

double E() {
	double v = 0;
	char c = str.at(pos);
	if (c == '+') {
		pos++;
		v = E() + T();
	}
	else if (c == '-') {
		pos++;
		v = E() - T();
	}
	else {
		pos++;
		v = T();
	}
	return v;
}

 double T() {
	double v = 0;
	char c = str.at(pos);
	if (c == '*') {
		pos++;
		v = T() * F();
	}
	else if (c == '/') {
		pos++;
		v = T() / F();
	}
	else {
		pos++;
		v = F();
	}
	return v;
}

 double F() {
	char c = str.at(pos);
	if (c == '(') {
		pos++;
		double v = E();
		c = str.at(pos);
		if (c == ')') {
			pos++;
			return v;
		}
	}
	else {
		string s = "";
		while (true) {
			c = str.at(pos);
			if (c >= '0' && c <= '9') {
				s += c;
				pos++;
			}
			else {
				break;
			}
		}

		return atoi(s.c_str());
	}
	return 0;
}



modified 9-Aug-18 2:57am.

AnswerRe: how to use recursive descent algorithm to compute an arithmetical expression? Pin
Richard MacCutchan8-Aug-18 20:50
protectorRichard MacCutchan8-Aug-18 20:50 
AnswerRe: how to use recursive descent algorithm to compute an arithmetical expression? Pin
Stefan_Lang8-Aug-18 22:07
memberStefan_Lang8-Aug-18 22:07 
QuestionRe: how to use recursive descent algorithm to compute an arithmetical expression? Pin
David Crow9-Aug-18 4:55
memberDavid Crow9-Aug-18 4:55 
AnswerRe: how to use recursive descent algorithm to compute an arithmetical expression? Pin
CPallini9-Aug-18 10:38
mvpCPallini9-Aug-18 10:38 
QuestionMovePrev() throwing 265926 error code (End Of RowsSet). Pin
Sampath5797-Aug-18 20:19
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AnswerRe: MovePrev() throwing 265926 error code (End Of RowsSet). Pin
Jochen Arndt7-Aug-18 21:52
mvpJochen Arndt7-Aug-18 21:52 
GeneralRe: MovePrev() throwing -2147217837 error code Pin
Sampath5797-Aug-18 22:23
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GeneralRe: MovePrev() throwing 265926 error code (End Of RowsSet). Pin
Jochen Arndt7-Aug-18 23:26
mvpJochen Arndt7-Aug-18 23:26 
GeneralRe: MovePrev() throwing 265926 error code (End Of RowsSet). Pin
Sampath5798-Aug-18 0:01
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GeneralRe: MovePrev() throwing 265926 error code (End Of RowsSet). Pin
Jochen Arndt8-Aug-18 0:29
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GeneralRe: MovePrev() throwing 265926 error code (End Of RowsSet). Pin
Sampath5798-Aug-18 3:19
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GeneralRe: MovePrev() throwing 265926 error code (End Of RowsSet). Pin
Jochen Arndt8-Aug-18 3:21
mvpJochen Arndt8-Aug-18 3:21 
GeneralRe: MovePrev() throwing -2147217837 error code. Pin
Sampath57912-Aug-18 1:36
memberSampath57912-Aug-18 1:36 
QuestionRe: MovePrev() throwing 265926 error code (End Of RowsSet). Pin
David Crow8-Aug-18 4:45
memberDavid Crow8-Aug-18 4:45 
AnswerRe: MovePrev() throwing 265926 error code (End Of RowsSet). Pin
Sampath5798-Aug-18 5:16
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QuestionRe: MovePrev() throwing 265926 error code (End Of RowsSet). Pin
David Crow9-Aug-18 4:56
memberDavid Crow9-Aug-18 4:56 
AnswerRe: MovePrev() throwing 265926 error code (End Of RowsSet). Pin
Stefan_Lang8-Aug-18 21:44
memberStefan_Lang8-Aug-18 21:44 

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