Mathematical expression translator - Printable Version +- Qbasicnews.com (http://qbasicnews.com/newforum) +-- Forum: QbasicNews.Com (http://qbasicnews.com/newforum/forum-3.html) +--- Forum: Challenges (http://qbasicnews.com/newforum/forum-10.html) +--- Thread: Mathematical expression translator (/thread-10109.html) |
Re: Mathematical expression translator - Ralph - 04-26-2008 What is a parse engine? Re: Mathematical expression translator - Frontrunner - 04-26-2008 Hi Ralph, The parser is the main routine you in this challenge and is also called a parse engine. Have a look at this link which will explain you some more on how a parser works: http://forums.devshed.com/other-programming-languages-139/how-does-an-interpreter-compiler-work-312483.html I hope that will help! Cheers, Frontrunner Re: Mathematical expression translator - Ralph - 04-29-2008 Thank you, Frontrunner, for your link. I now have a fair idea of what a parser is. Re: Mathematical expression translator - LPG - 04-29-2008 I tried this from QB > C. i made it do this:
the only error is that it searches from left to right so for:   (5^5)^5 it returns:   (pow( 5, 5) )pow( ,5) but for something like this:   5^5 it returns:   pow(5,5) it should look from the inside brackets to the outside brackets but i don't know how to do that.   LPG     Re: Mathematical expression translator - Frontrunner - 04-29-2008 You are very welcome Ralph, I am glad it helped! Hi LPG, If I may give you a tip ? Use an array to split the whole input string in to tokens. This makes it easier to keep track of symbols like brackets etc. and once you know where to place the pow statement you can simply change the array. So (5^5)^5 could look like this: Token$(1) = "(" Token$(2) = "5" Token$(3) = "^" Token$(4) = "5" Token$(5) = ")" Token$(6) = "^" Token$(7) = "5" To become pow((pow(5,5)),5) Token$(1) = "pow" + Token$(1) Token$(2) = "(pow(" + Token$(2) Token$(3) = "," Token$(4) = "5" Token$(5) = ")" + Token$(5) Token$(6) = "," Token$(7) = Token$(7) + ")" Note that all tokens which are ^ simply become a comma. The trick is to take track of the brackets! I hope that helps. And then one more tricky example when it comes to unary operators If -8 - -5 = 1 - -2 ^ 2 Then Becomes If -8 - -5= 1- -pow(2,2) Then Cheers, Frontrunner Re: Mathematical expression translator - wildcard - 04-30-2008 Interesting post there Frontrunner, I've not had much time last few days to work on my entry but was stuck at the brackets stage still too anyway, will hopefully get some time to finish it soon. Re: Mathematical expression translator - Frontrunner - 04-30-2008 Hi Wildcard, I hope it will help you to tackle the brackets. Have a nice day. Frontrunner Re: Mathematical expression translator - LPG - 04-30-2008 Thanks Frontrunner Re: Mathematical expression translator - Frontrunner - 04-30-2008 No problem, I hope it helped! Have a sunny day ;D Frontrunner Re: Mathematical expression translator - Frontrunner - 05-03-2008 I am not sure how many of you are working on this challenge but I came along this website which might be interesting for those who use FreeBasic and want to solve this challenge. http://www.runicsoft.com/fparser.php Cheers, Frontrunner |