Reverse polish calculator and reading from file

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November 15th, 2012, 01:30 PM

neuroh

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Reverse polish calculator and reading from file

I have a question about reverse polish calculator, here is the K&R reverse polish calculator. I had the calculator working but now I need it to take information from a file. Here is a quick sample of the input file.
#First example from the textbook
1 2 - 4 5 + *
#Compute 5!
1 2 3 4 5 ****
#Here come binomial(14, 9) and binomial(14, 5)
1 = 6 * 1 / = 7 * 2 / = 8 * 3 / = 9 * 4 / = 10 * 5 / = 11 * 6 / = 12 * 7 / = 13 * 8 / = 14 * 9 /
1 = 10 * 1 / = 11 * 2 / = 12 * 3 / = 13 * 4 / = 14 * 5 /

My code is below I have readLine which takes a # statement and just prints it since it is a comment. I was going to have my RPN function call the readLine function until EOF and fprintf it into a file and just loop like that but I am having problem implementing it. Can anyone give me some advice? And explain how exactly RPN, getop exactly work. Thanks.

Code:

//
//  main.c
//  inputReader
//

#include <stdio.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#define NUMBER '0'
#define MAXOP 100
#define MAXVAL 100
#define BUFSIZE 100
int sp = 0;
char out[256];
double val[MAXVAL];  /* value stack */
int buff[1024];
int i;
int run;
double pop(void);
void push(double f);
int getch(void);
void ungetch(int c);
char *RPNCalc()
{
	int type, iop2;
	double op1, op2, store_val;
	char s[MAXOP];
	char *outp = out;
	while ((type = getop(s)) != EOF) {
		switch (type) {
            case NUMBER:
                push(atof(s));
                break;
            case 'x':		//exchange top two stack items
                op1 = pop();
                op2 = pop();
                push(op1);
                push(op2);
                break;
            case 'R':
                push(store_val);
                break;
            case 'S':
                store_val = pop();
                break;
            case 0xd:		//skip cr
                break;
            case '+':
                push(pop() + pop());
                break;
            case '*':
                push(pop() * pop());
                break;
            case '-':
                op2 = pop();
                push(pop() - op2);
                break;
            case '/':
                op2 = pop();
                if (op2 != 0.0)
                    push(pop() / op2);
                else
                    outp += sprintf(outp, "error: zero divisor\n");
                break;
            case '=':	
                outp += sprintf(outp, "\t%.16g\n", op2 = pop());
                push(op2);
                break;
            case '\n':
                outp += sprintf(outp, "\t%.16g\n", op2 = pop());
                push(op2);
                return out;
                break;
            default:
                outp += sprintf(outp, "error: unknown command %s\n", s);
                break;
		}
	}
	return out;
}

int getop(char s[])
{
    int i, c;
    while ((s[0] = c = getch()) == ' ' || c == '\t')
        ;
    s[1] = '\0';
    if (!isdigit(c) && c != '.')
        return c;
    i = 0;
    if (isdigit(c))
        while (isdigit(s[++i] = c = getch()))
            ;
    if (c == '.')
        while (isdigit(s[++i] = c = getch())); s[i] = '\0';
    if (c != EOF)
        ungetch(c);
    return NUMBER;
}
char buf[BUFSIZE];
int bufp = 0;
int getch(void)
{
    return (bufp > 0) ? buf[--bufp] : getchar();
}
void ungetch(int c)
{
    if (bufp >= BUFSIZE)
        printf("ungetch: too many characters\n");
    else
        buf[bufp++] = c;
}
void push(double f)
{
    if (sp < MAXVAL)
        val[sp++] = f;
    else
        printf("error: stack full, can't push %g\n", f);
}
double pop(void)
{
    if (sp > 0)
        return val[--sp];
    else {
        printf("error: stack empty\n");
        return 0.0;
    }
}
int readLine(FILE *fp)
{
    i = 0;
    char c;
    while( (c = fgetc(fp)) != EOF && (c ) != '\n')
    {
        if ( c == '#' )
        {
            printf("%c", c);
            while( (c = fgetc(fp)) != EOF && c != '\n')
            {
                printf("%c", c);
            }
            printf("\n");
            return 0;
        }
        buff[i] = c;
        i++;
        run = 1;
        printf("%c", c);
    }
    printf("\n");
    return 0;
}
int main(int argc, const char * argv[])
{

    FILE *fp;
    if ((fp = fopen ("/Documents/buffthat/buffthat/input.txt", "rb")) == NULL)
        return -1;
    readLine(fp);
    readLine(fp);
    readLine(fp);
    return 0;
}

November 15th, 2012, 02:43 PM

dwise1_aol

Contributing User

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Yes, my first piece of advice for you is that you use code tags! Only then might we have some semblence of a chance of deciphering the code. As it is now, it's a huge unreadable mess.

November 15th, 2012, 02:47 PM

neuroh

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Join Date: Oct 2012

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Apologies

I am sorry, new to posting on this forum, was not sure on how to do it. Should of looked more into before posting. I am sorry for that.

November 15th, 2012, 05:19 PM

dwise1_aol

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Using blank lines to separate functions from each other, globals from functions, and variable declarations from code would also help. But the most essential is the code tags.

readLine reads a line from the file and puts it into buf.
RPNCalc reads from buf and outputs to out.

So then after a call to readLine, call RPNCalc and read the output from out.

November 15th, 2012, 07:57 PM

neuroh

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Question

Thank you for the advice, I had a follow up question. First would I just pass the buffer that I made over to rpncalc? Second should that buffer be an buffer of integers or characters? Also how would I change the while loop in RPNCalc to work with my readline? Should I have readLine return 1 for true if it read a line and 2 for if there is no more lines? Or do you have another suggestion on how to handle that. Sorry, I have a strong JAVA back ground but trying to jump into c and learn it.

November 16th, 2012, 01:23 AM

neuroh

Registered User

Join Date: Oct 2012

Posts: 11

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Help

Here what I modded to try and get input into rpn calculator. This does the job of reading the buffer backwards from getChar after using readLine. I tried it with a data line but it ran into some major errors. Was wondering if someone could explain to me the getop method in there. Thanks, and what I am doing wrong too please.

Code:


int readLine(FILE *fp)
{
    readVal = 0;
    i = 0;
    char c;
    while( (c = fgetc(fp)) != EOF && (c ) != '\n')
    {
        if ( c == '#' )
        {
            printf("%c", c);
            while( (c = fgetc(fp)) != EOF && c != '\n')
            {
                printf("%c", c);
            }
            printf("\n");
            return readVal;
        }
        readVal = 1;
        buff[i] = c;
        i++;
        run = 1;
        printf("%c", c);
    }
    printf("\n");
    return readVal;
}
int getChar(void)
{
    char b;
    if ( i > 0)
    {
        b = buff[--i];
    }
    return b;
}
int getop(char s[], FILE *fp)
{
    int i, c;
    while ((s[0] = c = getChar() ) == ' ' || c == '\t')
        ;
    s[1] = '\0';
    if (!isdigit(c) && c != '.')
        return c;
    i = 0;
    if (isdigit(c))
        while (isdigit(s[++i] = c = getChar()))
            ;
    if (c == '.')
        while (isdigit(s[++i] = c = getChar())); s[i] = '\0';
    if (c != EOF)
        ungetch(c);
    return NUMBER;
}

Reverse polish calculator and reading from file

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