hp_calc.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct Node {
	float value;
	struct Node *next;
};

int isNumber(char input[]);
void push(float n, struct Node **top);
float pop(struct Node **top);
void calcNumber(char operator[], struct Node **top);

int main()
{
	struct Node *top;
	char input[11];
	float number;

	while (strcmp(input, "q") != 0) {
		scanf("%s", input);

		if (isNumber(input) == 1) {
			number = strtof(input, NULL);
			push(number, &top);
		} else {
			calcNumber(input, &top);
		}
	}

	return 0;
}

void calcNumber(char operator[], struct Node **top) {
	float n2 = pop(top), n1 = pop(top), result;

	switch (operator[0]) {
		case '+':
			result = n1 + n2;
			break;
		case '-':
			result = n1 - n2;
			break;
		case '*':
			result = n1 * n2;
			break;
		case '/':
			result = n1 / n2;
			break;
	}

	push(result, top);

	printf("= %f\n", result);

}

void push(float n, struct Node **top) {
	struct Node *aux = (struct Node *) malloc(sizeof(struct Node));

	aux->value = n;

	if ((*top) == NULL) {
		(*top) = aux;
		(*top)->next = NULL;
	} else {
		aux->next = (*top);
		(*top) = aux;
	}
}

float pop(struct Node **top) {
	if ((*top) == NULL) {
		printf("Numero insuficiente\n");
		exit(0);
	}

	float number = (*top)->value;
	struct Node *aux = (struct Node *) malloc(sizeof(struct Node));

	aux = (*top);

	(*top) = (*top)->next;

	free(aux);

	return number;
}

int isNumber(char input[]) {
	if (strcmp(input, "+") == 0) {
		return 0;
	} else if (strcmp(input, "-") == 0) {
		return 0;
	} else if (strcmp(input, "*") == 0) {
		return 0;
	} else if (strcmp(input, "/") == 0) {
		return 0;
	} else {
		return 1;
	}
}