#include <math.h>
#include <string.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#define BUFFSIZE 1
#define MAXOP 1
#define MAXVAL 2
#define NUMBER 0
#define FUNCTION 255
void isfunction(char s[]);
void print(void);
void dupe(void);
void swap(void);
void clear(void);
int getch(void);
int getop(char s[]);
double pop(void);
void push(double);
void ungetch(int c);
char buf[BUFFSIZE];
int bufp=0;
int sp=0;
double val[MAXVAL];
double sto[26];
int last=0;
int main(void)
{
    int type;
    double op2;
    char s[MAXOP];
    while((type=getop(s))!=EOF)
    {
        last=type;
        switch(type)
        {
            case FUNCTION:
            {
                isfunction(s);
                break;
            }
            case NUMBER:
            {
                push(atof(s));
                break;
            }
            case'$':
            {
                print();
                break;
            }
            case'%':
            {
                op2=pop();
                push((int)pop()%(int)op2);
                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
                {
                    printf("Error: zero divisor.\n");
                }
                break;
            }
            case'\n':
            {
                printf("\t%.8g\n",pop());
                break;
            }
            default:
            {
                if(type>64&&type<91||type>96&&type<123)
                {
                    if(type>64&&type<91)
                    {
                        push(sto[(type-65)]);
                    }
                    else if(type>96&&type<123)
                    {
                        push(sto[(type-97)]);
                    }
                }
                else
                {
                    printf("Error: unknown command %s.\n",s);
                }
                break;
            }
        }
    }
    return 0;
}
void isfunction(char s[])
{
    double temp = 0;
    if(strcmp(s,"print")==0)
    {
        print();
    }
    else if(strcmp(s,"dupe")==0)
    {
        dupe();
    }
    else if(strcmp(s,"swap")==0)
    {
        swap();
    }
    else if(strcmp(s,"clear")==0)
    {
        clear();
    }
    else if(strcmp(s,"sin")==0)
    {
        push(sin(pop()));
    }
    else if(strcmp(s,"cos")==0)
    {
        push(cos(pop()));
    }
    else if(strcmp(s,"tan")==0)
    {
        push(tan(pop()));
    }
    else if(strcmp(s,"asin")==0)
    {
        push(asin(pop()));
    }
    else if(strcmp(s,"acos")==0)
    {
        push(acos(pop()));
    }
    else if(strcmp(s,"atan")==0)
    {
        push(atan(pop()));
    }
    else if(strcmp(s,"sinh")==0)
    {
        push(sinh(pop()));
    }
    else if(strcmp(s,"cosh")==0)
    {
        push(cosh(pop()));
    }
    else if(strcmp(s,"tanh")==0)
    {
        push(tanh(pop()));
    }
    else if(strcmp(s,"exp")==0)
    {
        push(exp(pop()));
    }
    else if(strcmp(s,"ln")==0)
    {
        push(log(pop()));
    }
    else if(strcmp(s,"log")==0)
    {
        push(log10(pop()));
    }
    else if(strcmp(s,"pow")==0)
    {
        temp=pop();
        push(pow(pop(),temp));
    }
    else if(strcmp(s,"sqrt")==0)
    {
        push(sqrt(pop()));
    }
    else if(strcmp(s,"ceil")==0)
    {
        push(ceil(pop()));
    }
    else if(strcmp(s,"floor")==0)
    {
        push(floor(pop()));
    }
    else if(strcmp(s,"fabs")==0)
    {
        push(fabs(pop()));
    }
    else if(strcmp(s,"ldexp")==0)
    {
        temp=pop();
        push(ldexp(pop(),temp));
    }
    else if(strcmp(s,"fmod")==0)
    {
        temp=pop();
        push(fmod(pop(),temp));
    }
    else
    {
        printf("isfunction: Error: unknown function.");
    }
}
void print(void)
{
    double retval;
    if(sp>0)
    {
        retval= val[sp];
        printf("%lf\n",retval);
    }
    else
    {
        printf("Error: the stack is empty\n");
    }
}
void dupe(void)
{
    double c;
    if(sp>0&&sp<MAXVAL)
    {
        c=val[(sp-1)];
        val[sp]=c;
        val[++sp]='\0';
    }
    else if(sp==0)
    {
        printf("Error: the is stack empty.\n");
    }
    else if(sp==MAXVAL)
    {
        printf("Error: the stack is full, cannot duplicate.\n");
    }
}
void swap(void)
{
    double c;
    if(sp>1)
    {
        c=val[(sp-2)];
        val[(sp-2)]=val[(sp-1)];
        val[(sp-1)]=c;

    }
    else
    {
        printf("Error: the stack is empty\n");
    }
}
void clear(void)
{
    sp=0;
}

int getch(void)
{
    return (bufp>0)?buf[--bufp]:getchar();
}
int getop(char s[])
{
    int i,c;
    while((s[0]=c=getch())==' '||c=='\t')
    {
        ;
    }
    s[1]='\0';
    i=0;
    if(isalpha(c))
    {
        while(isalpha(s[++i]=c=getch()))
        {
            ;
        }
        s[i]='\0';
        if(c!=EOF)
        {
            ungetch(c);
        }
        if(strlen(s)>1)
        {
            return FUNCTION;
        }
        else
        {
            return c;
        }
    }
    if(!isdigit(c)&&c!='.')
    {
        return c;
    }
    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;
}
double pop(void)
{
    if(sp>0)
    {
        return val[--sp];
    }
    else
    {
        printf("Error: the stack is empty. pop() returns:\n");
        return 0.;
    }
}
void push(double f)
{
    if(sp<MAXVAL)
    {
        val[sp++]=f;
    }
    else
    {
        printf("Error: the stack is full, cannot push %g.\n",f);
    }
}
void ungetch(int c)
{
    if(bufp>=BUFFSIZE)
    {
        printf("ungetch: Too many characters.\n");
    }
    else
    {
        buf[bufp++]=c;
    }
}