Fixed negative number issue

Makefile

@@ -0,0 +1,22 @@
+LFLAGS = -lm
+CFLAGS = -Wall
+CC = gcc
+
+BUILD_ROOT=.
+SDIR=$(BUILD_ROOT)/src
+BDIR=$(BUILD_ROOT)/build
+
+$(BDIR)/ee: $(BDIR) $(SDIR)/$(wildcard *.c)
+	$(CC) $(CFLAGS) $(LFLAGS) -o $@ src/ee.c
+
+$(BDIR):
+	mkdir $(BDIR)
+
+ee: $(BDIR)/ee
+
+clean:
+	$(MAKE) --no-print-directory -C $(SRC_DIR) clean
+	rm -rf $(BUILD_DIR)/*
+
+install:
+run: test

src/ee.c

@@ -0,0 +1,240 @@
+    #include "ee.h"
+int error = 0;
+void printStack(STACK);
+
+int
+main (const int argc, const char* argv[])
+{
+
+    STACK expr = NULL;
+
+    const char** endPtr = argv+argc,
+              ** arg    = argv+1   ;
+
+    char* fmt = (argc > 1)? (strcmp(argv[1],"-f")==0)? "%f\n" : "%g\n" : "%g\n";
+
+    while ((arg < endPtr) && (!error)){
+
+        if(isNum(*arg))
+            push(strtod(*arg, NULL), &expr);
+
+        else if (arrity(**arg))
+            push(evaluate(&expr, **arg), &expr);
+
+        else
+            error |= ERR_INVALID_INPUT;
+
+        arg += 1;
+
+    }
+
+    if (expr == NULL)
+        error |= ERR_NS_OPERANDS;
+
+    else if ((*expr).tail != NULL)
+        error |= ERR_NS_OPERATORS;
+
+    report(&expr, fmt);
+
+    return error;
+}
+
+int
+isNum(const char* query)
+{
+
+    /*
+     * If query is a string, isNum(query) iff query represents a number.
+     */
+
+    char *extra_char;
+    strtod(query, &extra_char);
+    return strcmp(extra_char, "") == 0;
+
+}
+
+int
+arrity(const char query)
+{
+    /*
+     * If query is a string corresponding to an operator in {+,x,-,/,^,!,%}, then
+     * arrity(query) is the number of operands required by the operator.
+     * If query is any other string, arrity(query) is zero.
+     */
+    return (query == '+')? 2:
+           (query == 'x')? 2:
+           (query == '-')? 2:
+           (query == '/')? 2:
+           (query == '^')? 2:
+           (query == '%')? 2:
+           (query == '!')? 1:
+           0;
+}
+
+
+double
+evaluate(STACK* target_stack, char operator)
+{
+    /*
+     * If target_stack is a pointer to a STACK and operator is
+     * a char corresponding to a supported operator,
+     * evaluate(target_stack,operator) is the result of
+     * applying the given operator to the appropriate number of
+     * operands from target_stack.
+     */
+    double value = 0;
+    //       a     = 0,
+    //       b     = 0;
+
+    double *_operands = operands(target_stack, arrity(operator));
+
+    switch (operator){
+
+        case '+' :
+            value = _operands[1] + _operands[0];
+            break;
+
+        case '-' :
+            value = _operands[1] - _operands[0];
+            break;
+
+        case 'x' :
+            value = _operands[1] * _operands[0];
+            break;
+
+        case '/' :
+            value = _operands[1] / _operands[0];
+            break;
+
+        case '^' :
+            value = pow(_operands[1],_operands[0]);
+            break;
+
+        case '!' :
+            if ( (*_operands != floor(*_operands)) || (*_operands < 0))
+                error |= ERR_INVALID_FACTORIAL;
+            else
+                value = fact(*_operands);
+
+            break;
+
+        case '%' :
+            value = ((int)_operands[1] % (int)_operands[0]);
+            break;
+
+        default :
+            break;
+    }
+    return value;
+}
+double*
+operands(STACK* target_stack, int size)
+{
+    /*
+     * if target_stack is a pointer to a STACK, and size is an integer
+     * corresponding to the number of operands desired,
+     * operands(target_stack,size) returns an array of operands and
+     * pops them off *target_stack.
+     */
+    double * const _operands = (double*)malloc(size*sizeof(double));
+
+    if ((*target_stack) == NULL)
+        error |= ERR_NS_OPERANDS;
+
+    double * tPtr   = _operands;
+    double * endPtr = _operands + size;
+    while ((tPtr < endPtr) && !error)
+    {
+        *tPtr = peek((target_stack));
+        pop(target_stack);
+
+        tPtr += 1;
+    }
+    return _operands;
+}
+
+double
+fact(int n)
+{
+    /*
+     * if n is an integer, fact(n) is 'n factorial'.
+     */
+    return (n==0)? 1 : n*fact(n-1);
+}
+
+void
+report(STACK* expr, char* fmt)
+{
+    /*
+     * reportErrors() prints error strings according to the value of global
+     * bitvector error if it is nonzero, or the result of evaluation if error
+     * is zero.
+     */
+
+    //printStack(expr);
+    if (error & ERR_INVALID_INPUT)
+        printf("Error: Unexpected input.\n");
+
+    else if (error & ERR_NS_OPERATORS)
+        printf("Error: insufficient operators.\n");
+
+    else if (error & ERR_NS_OPERANDS)
+        printf("Error: insufficient operands.\n");
+
+    else if (error & ERR_INVALID_FACTORIAL)
+        printf("Error: Factorials are only supported for positive integers.\n");
+
+    else
+        printf(fmt, peek(expr));
+}
+
+void
+printStack(STACK s)
+{
+    /* Given a stack, print "datum  tail"*/
+
+    while (s != NULL) {
+        printf("%g\t%p\n", s->datum, s->tail);
+        s = s->tail;
+    }
+    printf("%s\n", "-----");
+}
+
+void
+push(double datum, STACK* tail)
+{
+    /* Given a double value (datum), and a STACK (tail),
+     * push(datum,tail) is the STACK resulting from
+     * prepending datum to the STACK tail.
+     */
+     NODE* new_node = (NODE*)malloc(sizeof(NODE));
+     (*new_node).datum = datum;
+     (*new_node).tail  = *tail;
+     (*tail) = new_node;
+}
+
+void
+pop(STACK* target_stack)
+{
+    /* Given a STACK (target_stack), pop(target_stack)
+     * is the STACK resulting from the removal of the first
+     * item in target_stack;
+     */
+
+     STACK tail = NULL;
+
+     if ((*target_stack) != NULL){
+        tail = (*target_stack)->tail;
+        free(*target_stack);
+     }
+     (*target_stack) = tail;
+}
+
+double
+peek(STACK* target_stack)
+{
+    /* Given a STACK (target_stack), peek(STACK)
+     * is the first element's datum.
+     */
+     return (*target_stack)? (*target_stack)->datum : 0;
+}

src/ee.h

@@ -0,0 +1,36 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <ctype.h>
+#include <string.h>
+
+
+const int ERR_NS_OPERANDS       = 1;
+const int ERR_NS_OPERATORS      = 2;
+const int ERR_INVALID_INPUT     = 4;
+const int ERR_INVALID_FACTORIAL = 8;
+
+
+struct EE_STACK_NODE {
+    double datum;
+    struct EE_STACK_NODE* tail;
+};
+typedef struct EE_STACK_NODE NODE;
+typedef struct EE_STACK_NODE* STACK;
+
+void   push(double,STACK*);
+void   pop(STACK*);
+double  peek(STACK*);
+
+int     isNum(const char*);
+int     arrity(const char);
+
+double  evaluate(STACK*, char);
+double* operands(STACK*, int);
+double  fact(int n);
+
+void    report(STACK*,char*);
+
+
+
+