399 lines
10 KiB
C++
399 lines
10 KiB
C++
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/******************************************************************************
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COPYRIGHT(C) STEVEN DOUGHERTY 2011.
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COPYRIGHT(C) JONAS 'SORTIE' TERMANSEN 2011.
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This program is free software: you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the Free
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Software Foundation, either version 3 of the License, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details.
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You should have received a copy of the GNU General Public License along
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with this program. If not, see <http://www.gnu.org/licenses/>.
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calc.cpp
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A simple reverse polish calculator.
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******************************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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//Stack, pending standard library implementation. All in one file due to linking
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// annoyances with the makefile.
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template <typename T>
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class Stack {
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public:
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//Is its own iterator.
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/* MODIFIES: this.
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* EFFECTS: Self-iterator: sets to first element and returns it.
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*/
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const T *begin() {
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currentIter = head;
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return next();
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}
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/* MODIFIES: this.
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* EFFECTS: Self-iterator: returns element from the list and advances.
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* If all elements have been iterated, returns NULL. Does not
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* have invalidation - be careful!
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*/
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const T *next() {
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if (!currentIter) return NULL;
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const T *element = currentIter->o;
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currentIter = currentIter->next;
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return element;
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}
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/* EFFECTS: Returns true if stack is empty, false otherwise.
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*/
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bool isEmpty() const {
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return !head;
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}
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/* MODIFIES: this.
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* EFFECTS: Pushes o onto the top of the stack.
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*/
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void push(T *o) {
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head = new node(head, o);
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}
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/* MODIFIES this
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* EFFECTS Pops and returns the top element. Returns NULL if empty.
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*/
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T *pop() {
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if (isEmpty()) return NULL;
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node *oldHead = head;
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T *element = oldHead->o;
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head = oldHead->next;
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delete oldHead;
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return element;
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}
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Stack() : head(NULL) , currentIter(NULL) {}
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Stack(const Stack &s) : head(NULL) , currentIter(NULL) {
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s.begin();
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copyAll(s.head);
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}
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Stack &operator=(const Stack &s) {
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if (this == &s) return;
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removeAll();
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copyAll(s.head);
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}
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~Stack() {
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removeAll();
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}
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private:
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struct node {
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node(node *next, T *o) : next(next), o(o) {}
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node *next;
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T *o;
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};
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node *head;
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node *currentIter;
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/* MODIFIES: this.
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* EFFECT: called by copy constructor and operator= to copy elements
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* following from the given node into the local instance.
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*/
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void copyAll(const node *n) {
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if (n) {
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copyAll(n->next);
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push(new T(*(n->o)));
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}
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}
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void removeAll() {
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while (!isEmpty()) delete pop();
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}
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};
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/* MODIFIES: stack.
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* EFFECTS: Pushes value onto the stack.
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*/
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void push(long *value, Stack<long> &stack) {
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stack.push(value);
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}
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/* MODIFIES: stack.
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* EFFECTS: Pushes value onto the stack.
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*/
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void push(long value, Stack<long> &stack) {
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stack.push(new long(value));
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}
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/* MODIFIES: operand, stack, standard output.
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* EFFECTS: Attempts to set operand to the top value on the stack. If there
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* are no operands on the stack, prints an error message and aborts
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* the process with exit code 1.
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*/
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void pop(long *&operand, Stack<long> &stack) {
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if (stack.isEmpty()) {
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printf("%s: not enough operands\n", program_invocation_name);
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exit(1);
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}
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operand = stack.pop();
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}
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/* MODIFIES: operand1, operand2, stack, standard output.
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* EFFECTS: Attempts to remove two operands from the top of the stack, setting
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* operand1 to the first one removed and operand2 to the second. If
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* there are fewer than two enough operands on the stack, prints
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* an error message and aborts the process with exit code 1.
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*/
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void popTwo(long *&operand1, long *&operand2, Stack<long> &stack) {
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pop(operand1, stack);
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pop(operand2, stack);
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}
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/* MODIFIES: stack, standard output.
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* EFFECTS: Attempts to replace the top two operands on the stack with the
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* result returned by func(first, second).
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*/
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//Lambda functions would be wonderful for calling this function.
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//http://www2.research.att.com/~bs/C++0xFAQ.html#lambda
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void apply(long(*func)(long, long), Stack<long> &stack) {
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long *operand1, *operand2;
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popTwo(operand1, operand2, stack);
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push(func(*operand1, *operand2), stack);
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delete operand1;
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delete operand2;
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}
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/* EFFECTS: Returns first + second.
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*/
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long add(long first, long second) { return first + second; }
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/* EFFECTS: Returns subtracting "the first number from the second" (pg. 5)
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*/
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long subtract(long first, long second) { return second - first; }
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/* EFFECTS: Returns first * second.
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*/
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long multiply(long first, long second) { return first * second; }
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/* MODIFIES: stack, standard output.
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* EFFECTS: Attempts to replace the top two operands on the stack with the
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* result of dividing the second one by the first.
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* If the first number is zero, prints an division by zero error and
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* exits the process with exit code 1.
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*/
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void divide(Stack<long> &stack) {
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/* Can't use apply for this because it requires a check for the
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* denominator being zero. It could have an error-checking function
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* pointer, but that would muddy things as no other operators have such
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* conditions.
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*/
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long *first, *second;
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popTwo(first, second, stack);
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if (*first == 0) {
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printf("%s: division by zero\n", program_invocation_name);
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exit(1);
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}
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push(*second / *first, stack);
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delete first;
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delete second;
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}
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/* MODIFIES: stack, standard output.
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* EFFECTS: Attempts to negate the top element on the stack.
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*/
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void negate(Stack<long> &stack) {
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long *operand;
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pop(operand, stack);
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push(-(*operand), stack);
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delete operand;
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}
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/* MODIFIES: stack, standard output.
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* EFFECTS: Attempts to push a copy of the top element on top of the already
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* existing one.
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*/
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void duplicate(Stack<long> &stack) {
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long *operand;
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pop(operand, stack);
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//Dereferencing creates new instance.
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push(*operand, stack);
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push(operand, stack);
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}
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/* MODIFIES: stack, standard output.
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* EFFECTS: Attempts to reverse the first two elements on the stack.
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*/
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void reverse(Stack<long> &stack) {
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long *first, *second;
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popTwo(first, second, stack);
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//Push the former first before the former second.
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push(first, stack);
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push(second, stack);
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}
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/* MODIFIES: standard output.
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* EFFECTS: Prints the first element on the stack to standard output, followed
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* by a newline.
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*/
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void print(Stack<long> &stack) {
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long *operand;
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pop(operand, stack);
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printf("%li\n", *operand);
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push(operand, stack);
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}
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/* MODIFIES: stack.
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* EFFECTS: Empties the stack.
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*/
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void clear(Stack<long> &stack) {
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while (!stack.isEmpty()) delete stack.pop();
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}
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/* MODIFIES: standard output.
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* EFFECTS: Prints all the elements on the stack, from top to bottom, each
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* separated by a single space. No trailing space. Ends with newline.
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*/
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void printAll(Stack<long> &stack) {
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if (!stack.isEmpty()) {
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const long *element = stack.begin();
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do {
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printf("%li", *element);
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} while ((element = stack.next()) && printf(" "));
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}
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printf("\n");
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}
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/* MODIFIES: standard output.
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* EFFECTS: Prints usage information and returns 0.
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*/
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int printUsage(const char* argv0) {
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printf("Usage: %s [--help] [--usage] COMMAND ...\n", argv0);
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printf("%s is a Reverse Polish Notation integer calculator.\n", argv0);
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printf("\n");
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printf(" --help, --usage Display this help and exit\n");
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printf("\n");
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printf("%s supports the following commands:\n", argv0);
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printf("Any integers supplied are pushed onto the stack and can be given in decimal\n");
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printf("(default), octal with a leading 0, or hexadecimal with a leading 0x. Numbers\n");
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printf("can be prefixed with + or - to specify positive or negative, respectively.\n");
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printf("The operators +, -, *, and / pop the top two elements and push the result of\n");
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printf("<second> <operator> <first> to the stack. The top element is printed on exit\n");
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printf("unless a print command is given or an error occurs. Also,\n");
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printf(" a: prints all elements from first to last.\n");
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printf(" c: clears the stack.\n");
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printf(" d: duplicates the top element.\n");
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printf(" n: negates the top element.\n");
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printf(" p: prints the top element.\n");
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printf(" r: reverses the order of the top two elements.\n");
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printf("\n");
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printf("Examples:\n");
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printf(" %s 2 2 +\n", argv0);
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printf(" %s 0xCAFE42 0777 *\n", argv0);
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return 0;
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}
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int main(int argc, char *argv[]) {
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//If no arguments, --usage, or --help.
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if (argc == 1 ||
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(argc > 1 && (!strcmp(argv[1], "--usage") ||
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!strcmp(argv[1], "--help"))))
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return printUsage(argv[0]);
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Stack<long> stack;
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bool printedAnything = false;
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//Skip program name in arguments list.
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for (int i = 1; i < argc; i++) {
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char *endPtr;
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//Allow input in decimal, octal, or hex.
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long numberInput = strtol(argv[i], &endPtr, 0);
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//Make sure the string is a number and not empty.
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if (*argv[i] && !(*endPtr)) {
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push(numberInput, stack);
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continue;
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}
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/* Input was not a valid number, attempt to parse as operator.
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* Anything other than one character is not a valid operator.
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*/
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if (strlen(argv[i]) == 1) {
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switch (argv[i][0]) {
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case '+':
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//Add
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apply(add, stack);
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continue;
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case '-':
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//Subtract
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apply(subtract, stack);
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continue;
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case '*':
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//Multiply
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apply(multiply, stack);
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continue;
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case '/':
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//Divide
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divide(stack);
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continue;
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case 'n':
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//Negate
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negate(stack);
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continue;
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case 'd':
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//Duplicate
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duplicate(stack);
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continue;
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case 'r':
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//Reverse
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reverse(stack);
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continue;
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case 'p':
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//Print
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print(stack);
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printedAnything = true;
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continue;
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case 'c':
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//Clear
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clear(stack);
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continue;
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case 'a':
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//Print-all
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printAll(stack);
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printedAnything = true;
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continue;
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}
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}
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printf("%s: unsupported command: %s\n", program_invocation_name, argv[i]);
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exit(1);
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}
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if ( !printedAnything && !stack.isEmpty() ) {
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print(stack);
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}
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return 0;
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}
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