Thread: Infix, Postfix, Pseudo-Calculator using Stack ADT

  1. 09-06-2006 #1
    sangken
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    Talking Infix, Postfix, Pseudo-Calculator using Stack ADT

    basically, what i want to do is create a generic pseudo-calculator which takes a string containing a mathematical expression in standard or infix form, converts it to postfix form, convert the characters to respective int values, then perform the calculation, and finally output the result..

    i already have the code which converts infix to postfix using stack ADT, and the code to "calculate" the postfix using stack also...

    can anyone give me a pseudocode for the main function?? my main problem is converting the characters in the string to their respective mathematical tokens.

    thanks!!!
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  2. 09-06-2006 #2
    quzah
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    You could always try the search button, since every few months some one posts nearly this same topic.


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  3. 09-06-2006 #3
    sangken
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    Well, i tried searching and here's what i got: (using infix postfix keywords)

    Sorry - no matches. Please try some different terms.

    oh well, i guess i'll just wait till some1 takes pity on lil me...
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  4. 09-06-2006 #4
    quzah
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    You're a liar.

    Searching with both infix and postfix gives you this (two pages of results).
    Searching with just infix gives you this (two pages of results).
    Searching with just postfix gives you this (three pages of results).

    I hate liars.


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  5. 09-06-2006 #5
    sangken
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    Jeeze, you really have this habbit of calling people BAD names... i swear i searched and it came up with the result.... why dont you try searching for someting you're sure doesnt exist in this forum and i'll bet a million bucks that's the error message you'll get...

    hmm, i think i might have included a comma "," on my search or sumthin... tis funny...
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  6. 09-06-2006 #6
    sangken
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    Anyway, thanks for the links and for calling me a liar...
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  7. 09-06-2006 #7
    sangken
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    Hahaha! stupid me!!! i accidentally searched on the "Search this Thread" search field... dummy.. LOL
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  8. 09-06-2006 #8
    Cactus_Hugger
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    If you Google "infix postfix conversion", this page is yielded as the top result. I used it when I wrote my calculator, and it was a wonderful resource. The Wikipedia article on Reverse Polish Notation also helped me a lot.
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  9. 09-07-2006 #9
    linuxdude
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    I woulndn't conver to ints if I were you, unless you want to be inaccurate
  10. 09-08-2006 #10
    jafet
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    If I were to be doing this, I'd add in builtin support for large numbers; maybe with GMP, though I could go homebrew if I wanted to. Ints are generally inadequate.

    You might want to look into finite state machines, lexer programs and tokenization in general to parse the expressions. For such a program the Shunting Yard algorithm to convert infix notation to postfix, coupled with Reverse Polish Notation, should be all you need, really; once you're done with the tokenization bit that is. Go search on Wikipedia; I'll bet you "a million bucks" you will find more than you ever need.
    Code:
    #include <stdio.h>

void J(char*a){int f,i=0,c='1';for(;a[i]!='0';++i)if(i==81){
puts(a);return;}for(;c<='9';++c){for(f=0;f<9;++f)if(a[i-i%27+i%9
/3*3+f/3*9+f%3]==c||a[i%9+f*9]==c||a[i-i%9+f]==c)goto e;a[i]=c;J(a);a[i]
='0';e:;}}int main(int c,char**v){int t=0;if(c>1){for(;v[1][
t];++t);if(t==81){J(v[1]);return 0;}}puts("sudoku [0-9]{81}");return 1;}
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