[calc.git] / parser.c

#include <malloc.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>

#include "debug.h"

#include "parser.h"

/* compare codes */

int codecmp (char *ref, char *str)
{
    int sig;

    while (*ref != '\0') {
        if (*ref == '\t') {
             sig = (*str == '.') ? -1 : ((*str >= '0') && (*str <= '9'));
        } else {
            sig = *str - *ref;
        }
        if (sig != 0) {
            return (sig > 0) ? 1 : -1;
        }
        str++;
        ref++;
    }

    return 0;
}

/* allocate new element */

element_t *newelement (func_t function, int nbops, int prio)
{
    element_t *new = (element_t *) calloc (1, sizeof (element_t));
    if (new == NULL) {
        VERBOSE (ERROR, fprintf (stderr, "can't allocate memory\n"));
        return NULL;
    }
    new->func = function;
    new->nbops = nbops;
    new->prio = prio;

    return new;
}

/* desallocate element */

void delelement (element_t *root)
{
    int i;
    if ((root != NULL) && (root != ERROR_OP)) {
        for (i = 0; i < root->nbops; i++) {
            if ((root->ops[i] != NULL) && (root->ops[i] != ERROR_OP)) {
                delelement (root->ops[i]);
            }
        }
        free (root);
    }
}

/* functions */

#define NB_OPERATORS 6

keyword_t operators[NB_OPERATORS] = {
    { "+\t", Add, 2, 1, 1},
    { "-\t", Sub, 2, 1, 1},
    { "*",   Mul, 2, 1, 2},
    { "/",   Div, 2, 1, 2},
    { "%",   Mod, 2, 1, 3},
    { "^",   Pow, 2, 1, 4}
};

#define NB_FUNCTIONS 9
keyword_t functions[NB_FUNCTIONS] = {
    { "sqrt", Sqr, 1, 4, 5},
    { "pow",  Pow, 2, 3, 5},
    { "cos",  Cos, 1, 3, 5},
    { "sin",  Sin, 1, 3, 5},
    { "atan", Atan, 1, 4, 5},
    { "exp",  Exp, 1, 3, 5},
    { "log",  Log, 1, 3, 5},
    { "quit", Quit, 0, 4, 5},
    { "help", Help, 0, 4, 5}
};

#define NB_CONSTANTS 2
keyword_t constants[NB_CONSTANTS] = {
    { "e",  E,  0, 1, 5},
    { "pi", Pi, 0, 2, 5}
};

/* subparser function */

element_t *subparser (element_t **proot, char **pstr, func_t func, int nbops, int prio)
{
    element_t *new = newelement (func, nbops, prio);
    if (new == NULL) {
        return ERROR_OP;
    }
    new->ops[0] = *proot;
    new->ops[1] = parser (*pstr, pstr, new->prio);
    if (new->ops[1] == ERROR_OP) {
        delelement (new);
        *proot = NULL;
        return ERROR_OP;
    }
    *proot = newelement (Val, 1, 5);
    if (*proot == NULL) {
        delelement (new);
        return ERROR_OP;
    }
    (*proot)->ops[0] = new;

    return *proot;
}

/* parser function */

element_t *parser (char *str, char **next, int prio)
{
    element_t *root = NULL;
    int i;

    VERBOSE (DEBUG, fprintf (stdout, "Starting parsing\n"));

    /* main loop */
    while (*str != '\0') {
        int found = 0;
        element_t *new = NULL;
        VERBOSE (INFO, fprintf (stdout, "Processing: %s\n", str));

        /* skip spaces and tabs */

        if ((*str == ' ') || (*str == '\t')) {
            str++;
            continue;
        }

        /* check for open bracket */

        if (*str == '(') {
            VERBOSE (DEBUG, fprintf (stdout, "start processing bracket\n"));
            if (root) {
                do {
                    found = 0;
                    new = parser (str + 1, &str, 0);
                    if (new == ERROR_OP) {
                        delelement (root);
                        return ERROR_OP;
                    }
                    for (i = 0; i < root->nbops; i++) {
                        if (root->ops[i] == NULL) {
                            root->ops[i] = new;
                            found = 1;
                            break;
                        }
                    }
                    if (!found) {
                        delelement (new);
                        delelement (root);
                        return ERROR_OP;
                    }
                } while (*str == ',');
            } else {
                root = newelement (Val, 1, 5);
                if (root == NULL) {
                    return ERROR_OP;
                }
                new = parser (str + 1, &str, 0);
                if ((new == ERROR_OP) || (*str == ',')) {
                    delelement (new);
                    delelement (root);
                    return ERROR_OP;
                }
                root->ops[0] = new;
            }
            str++;
            VERBOSE (DEBUG, fprintf (stdout, "stop processing bracket\n"));
            continue;
        }

        /* check for closing bracket or koma */

        if ((*str == ')') || (*str == ',')) {
            if (next != NULL) {
                *next = str;
            }
            return root;
        }

        /* look for operators */

        for (i = 0; i < NB_OPERATORS; i++) {
            keyword_t *operator = operators + i;
            if (codecmp (operator->keyword, str) == 0) {
                VERBOSE (DEBUG, fprintf (stdout, "start processing operator\n"));
                if (root) {
                    if ((prio) && (prio > operator->prio)) {
                        VERBOSE (DEBUG, fprintf (stdout, "stop because operator priority\n"));
                        *next = str;
                        return root;
                    }
                    str += operator->offset;
                    VERBOSE (INFO, fprintf (stdout, "Oper: %d\n", operator->func));
                    if (subparser (&root, &str, operator->func, operator->nbops, operator->prio) == ERROR_OP) {
                        delelement (root);
                        return ERROR_OP;
                    }
                } else if (*str == '-') {
                    new = newelement (Sig, 1, 9);
                    if (new == NULL) {
                        return ERROR_OP;
                    }
                    root = new;
                } else {
                    return ERROR_OP;
                }
                found = 1;
                VERBOSE (DEBUG, fprintf (stdout, "stop processing operator\n"));
                break;
            }
        }
        if (found) {
            continue;
        }

        /* look for functions */

        for (i = 0; i < NB_FUNCTIONS; i++) {
            keyword_t *function = functions + i;
            if (codecmp (function->keyword, str) == 0) {
                VERBOSE (DEBUG, fprintf (stdout, "start processing function\n"));
                if (root == NULL) {
                    VERBOSE (INFO, fprintf (stdout, "Func: %d\n", function->func));
                    new = newelement (function->func, function->nbops, function->prio);
                    if (new == NULL) {
                        return ERROR_OP;
                    }
                    root = new;
                } else {
                    delelement (root);
                    return ERROR_OP;
                }
                str += function->offset;
                found = 1;
                VERBOSE (DEBUG, fprintf (stdout, "stop processing function\n"));
                break;
            }
        }
        if (found) {
            continue;
        }

        /* look for constant */

        for (i = 0; i < NB_CONSTANTS; i++) {
            keyword_t *constant = constants + i;
            if (codecmp (constant->keyword, str) == 0) {
                VERBOSE (DEBUG, fprintf (stdout, "start processing constant\n"));
                if (root == NULL) {
                    VERBOSE (INFO, fprintf (stdout, "Func: %d\n", constant->func));
                    new = newelement (constant->func, constant->nbops, constant->prio);
                    if (new == NULL) {
                        return ERROR_OP;
                    }
                    root = new;
                } else {
                    delelement (root);
                    return ERROR_OP;
                }
                str += constant->offset;
                found = 1;
                VERBOSE (DEBUG, fprintf (stdout, "stop processing constant\n"));
                break;
            }
        }
        if (found) {
            continue;
        }

        /* look for number */

        if (((*str >= '0') && (*str <= '9')) ||
            (*str == '.') || (*str == '+') || (*str == '-')) {
            VERBOSE (DEBUG, fprintf (stdout, "start processing value\n"));
            char *pt;
            double value = strtod (str, &pt);
            VERBOSE (INFO, fprintf (stdout, "Value: %f\n", value));
            if (str != pt) {
                if (root == NULL) {
                    new = newelement (Val, 1, 5);
                    if (new == NULL) {
                        return ERROR_OP;
                    }
                    new->value = value;
                    root = new;
                    str = pt;
                } else if (root->func == Val) {
                    if ((*str == '+') || (*str == '-')) {
                        if ((prio) && (prio > 1)) {
                            VERBOSE (DEBUG, fprintf (stdout, "stop because operator priority\n"));
                            *next = str;
                            return root;
                        }
                        if (subparser (&root, &str, Add, 2, 1) == ERROR_OP) {
                            delelement (root);
                            return ERROR_OP;
                        }
                    } else {
                        delelement (root);
                        return ERROR_OP;
                    }
                } else {
                    delelement (root);
                    return ERROR_OP;
                }
                found = 1;
            }
            VERBOSE (DEBUG, fprintf (stdout, "stop processing value\n"));
        }

        /* error */

        if (!found) {
            delelement (root);
            return ERROR_OP;
        }

    }

    if (next != NULL) {
        *next = str;
    }

    return root;
}

/* print element tree */

void print_element (element_t *root, int level)
{
    char *func = NULL;
    int i;

    if ((root == NULL) || (root == ERROR_OP)) {
        return;
    }

    for (i = 0; i < level; i++) {
        fprintf (stdout, " ");
    }

    switch (root->func) {
    case Val: func = "Value"; break;
    case Sig: func = "Sign"; break;
    case Add: func = "Addition"; break;
    case Sub: func = "Subtraction"; break;
    case Mul: func = "Multiplication"; break;
    case Div: func = "Division"; break;
    case Mod: func = "Modulo"; break;
    case Pow: func = "Power"; break;
    case Sqr: func = "Square Root"; break;
    case Cos: func = "Cosine"; break;
    case Sin: func = "Sine"; break;
    case Atan: func = "Arc Tangent"; break;
    case Log: func = "Logarithm"; break;
    case Exp: func = "Exponantial"; break;
    case Quit: func = "Quit"; break;
    case Help: func = "Help"; break;
    case Pi: func = "Pi"; break;
    case E: func = "E"; break;
    }

    fprintf (stdout, "Function: %s\n", func);

    if ((root->func == Val) && (root->ops[0] == NULL)) {
        for (i = 0; i < level; i++) {
            fprintf (stdout, " ");
        }
        fprintf (stdout, "value: %f\n", root->value);
    } else {
        for (i = 0; i < root->nbops; i++) {
            print_element (root->ops[i], level + 1);
        }
    }
}

/* quit function */

void quit (void)
{
    fprintf (stdout, "bye\n");
    exit (0);
}

/* help message */

void help (void)
{
    fprintf (stdout, "calc is a simple calculator\n\n");
    fprintf (stdout, "supported operators:\n");
    fprintf (stdout, " + - * / %% ^\n\n");
    fprintf (stdout, "supported functions:\n");
    fprintf (stdout, " pow sqrt cos sin atan log exp\n\n");
    fprintf (stdout, "miscellaneous functions:\n");
    fprintf (stdout, " quit help\n\n");
    fprintf (stdout, "supported constants:\n");
    fprintf (stdout, " e pi\n");
}

/* evaluate element tree */

#define MASK_SUB 0x1
#define MASK_DIV 0x2

double evaluate_element (element_t *root, char mask)
{
    double op0 = 0, op1 = 0;
    char nextmask = mask;

    if ((root == NULL) || (root == ERROR_OP)) {
        VERBOSE (WARNING, fprintf (stdout, "error while evaluating\n"));
        return 0;
    }

    /* mask to manage sub operator sub and div */
    switch (root->func) {
    case Add:
        nextmask &= ~MASK_SUB;
        nextmask &= ~MASK_DIV;
        break;
    case Sub:
        nextmask |= MASK_SUB;
        nextmask &= ~MASK_DIV;
        break;
    case Mul:
        nextmask &= ~MASK_DIV;
        break;
    case Div:
        nextmask |= MASK_DIV;
        break;
    default:
        nextmask = mask;
    }

    switch (root->func) {
    case Val:
    case Sig:
        op0 = (root->ops[0]) ? evaluate_element (root->ops[0], nextmask) : root->value;
        break;
    case Add:
    case Sub:
    case Mul:
    case Div:
    case Mod:
    case Pow:
        if (root->ops[1]) {
            op1 = evaluate_element (root->ops[1], nextmask);
        } else {
            VERBOSE (WARNING, fprintf (stdout, "error while evaluating (op[1])\n"));
            return 0;
        }
        /* fallthrough */
    case Sqr:
    case Cos:
    case Sin:
    case Atan:
    case Log:
    case Exp:
        if (root->ops[0]) {
            op0 = evaluate_element (root->ops[0], 0);
        } else {
            VERBOSE (WARNING, fprintf (stdout, "error while evaluating (op[0])\n"));
            return 0;
        }
        break;
    case Quit:
    case Help:
    case Pi:
    case E:
        break;
    }

    switch (root->func) {
    case Val: return op0;
    case Sig: return -op0;
    case Add: return ((mask & MASK_SUB) == 0) ? op0 + op1 : op0 - op1;
    case Sub: return ((mask & MASK_SUB) == 0) ? op0 - op1 : op0 + op1;
    case Mul: return ((mask & MASK_DIV) == 0) ? op0 * op1 : op0 / op1;
    case Div: return ((mask & MASK_DIV) == 0) ? op0 / op1 : op0 * op1;
    case Mod: return fmod (op0, op1);
    case Pow: return pow (op0, op1);
    case Sqr: return sqrt (op0);
    case Cos: return cos (op0);
    case Sin: return sin (op0);
    case Atan: return atan (op0);
    case Log: return log (op0);
    case Exp: return exp (op0);
    case Quit: quit (); break;
    case Help: help (); break;
    case Pi: return M_PI;
    case E: return M_E;
    }

    return 0;
}

/* vim: set ts=4 sw=4 et: */
Commit	Line	Data
	1	#include <malloc.h>
	2	#include <math.h>
	3	#include <stdio.h>
	4	#include <stdlib.h>
	5
	6	#include "debug.h"
	7
	8	#include "parser.h"
	9
	10	/* compare codes */
	11
	12	int codecmp (char ref, char str)
	13	{
	14	int sig;
	15
	16	while (*ref != '\0') {
	17	if (*ref == '\t') {
	18	sig = (str == '.') ? -1 : ((str >= '0') && (*str <= '9'));
	19	} else {
	20	sig = str - ref;
	21	}
	22	if (sig != 0) {
	23	return (sig > 0) ? 1 : -1;
	24	}
	25	str++;
	26	ref++;
	27	}
	28
	29	return 0;
	30	}
	31
	32	/* allocate new element */
	33
	34	element_t *newelement (func_t function, int nbops, int prio)
	35	{
	36	element_t new = (element_t ) calloc (1, sizeof (element_t));
	37	if (new == NULL) {
	38	VERBOSE (ERROR, fprintf (stderr, "can't allocate memory\n"));
	39	return NULL;
	40	}
	41	new->func = function;
	42	new->nbops = nbops;
	43	new->prio = prio;
	44
	45	return new;
	46	}
	47
	48	/* desallocate element */
	49
	50	void delelement (element_t *root)
	51	{
	52	int i;
	53	if ((root != NULL) && (root != ERROR_OP)) {
	54	for (i = 0; i < root->nbops; i++) {
	55	if ((root->ops[i] != NULL) && (root->ops[i] != ERROR_OP)) {
	56	delelement (root->ops[i]);
	57	}
	58	}
	59	free (root);
	60	}
	61	}
	62
	63	/* functions */
	64
	65	#define NB_OPERATORS 6
	66
	67	keyword_t operators[NB_OPERATORS] = {
	68	{ "+\t", Add, 2, 1, 1},
	69	{ "-\t", Sub, 2, 1, 1},
	70	{ "*", Mul, 2, 1, 2},
	71	{ "/", Div, 2, 1, 2},
	72	{ "%", Mod, 2, 1, 3},
	73	{ "^", Pow, 2, 1, 4}
	74	};
	75
	76	#define NB_FUNCTIONS 9
	77	keyword_t functions[NB_FUNCTIONS] = {
	78	{ "sqrt", Sqr, 1, 4, 5},
	79	{ "pow", Pow, 2, 3, 5},
	80	{ "cos", Cos, 1, 3, 5},
	81	{ "sin", Sin, 1, 3, 5},
	82	{ "atan", Atan, 1, 4, 5},
	83	{ "exp", Exp, 1, 3, 5},
	84	{ "log", Log, 1, 3, 5},
	85	{ "quit", Quit, 0, 4, 5},
	86	{ "help", Help, 0, 4, 5}
	87	};
	88
	89	#define NB_CONSTANTS 2
	90	keyword_t constants[NB_CONSTANTS] = {
	91	{ "e", E, 0, 1, 5},
	92	{ "pi", Pi, 0, 2, 5}
	93	};
	94
	95	/* subparser function */
	96
	97	element_t subparser (element_t proot, char *pstr, func_t func, int nbops, int prio)
	98	{
	99	element_t *new = newelement (func, nbops, prio);
	100	if (new == NULL) {
	101	return ERROR_OP;
	102	}
	103	new->ops[0] = *proot;
	104	new->ops[1] = parser (*pstr, pstr, new->prio);
	105	if (new->ops[1] == ERROR_OP) {
	106	delelement (new);
	107	*proot = NULL;
	108	return ERROR_OP;
	109	}
	110	*proot = newelement (Val, 1, 5);
	111	if (*proot == NULL) {
	112	delelement (new);
	113	return ERROR_OP;
	114	}
	115	(*proot)->ops[0] = new;
	116
	117	return *proot;
	118	}
	119
	120	/* parser function */
	121
	122	element_t parser (char str, char **next, int prio)
	123	{
	124	element_t *root = NULL;
	125	int i;
	126
	127	VERBOSE (DEBUG, fprintf (stdout, "Starting parsing\n"));
	128
	129	/* main loop */
	130	while (*str != '\0') {
	131	int found = 0;
	132	element_t *new = NULL;
	133	VERBOSE (INFO, fprintf (stdout, "Processing: %s\n", str));
	134
	135	/* skip spaces and tabs */
	136
	137	if ((str == ' ') \|\| (str == '\t')) {
	138	str++;
	139	continue;
	140	}
	141
	142	/* check for open bracket */
	143
	144	if (*str == '(') {
	145	VERBOSE (DEBUG, fprintf (stdout, "start processing bracket\n"));
	146	if (root) {
	147	do {
	148	found = 0;
	149	new = parser (str + 1, &str, 0);
	150	if (new == ERROR_OP) {
	151	delelement (root);
	152	return ERROR_OP;
	153	}
	154	for (i = 0; i < root->nbops; i++) {
	155	if (root->ops[i] == NULL) {
	156	root->ops[i] = new;
	157	found = 1;
	158	break;
	159	}
	160	}
	161	if (!found) {
	162	delelement (new);
	163	delelement (root);
	164	return ERROR_OP;
	165	}
	166	} while (*str == ',');
	167	} else {
	168	root = newelement (Val, 1, 5);
	169	if (root == NULL) {
	170	return ERROR_OP;
	171	}
	172	new = parser (str + 1, &str, 0);
	173	if ((new == ERROR_OP) \|\| (*str == ',')) {
	174	delelement (new);
	175	delelement (root);
	176	return ERROR_OP;
	177	}
	178	root->ops[0] = new;
	179	}
	180	str++;
	181	VERBOSE (DEBUG, fprintf (stdout, "stop processing bracket\n"));
	182	continue;
	183	}
	184
	185	/* check for closing bracket or koma */
	186
	187	if ((str == ')') \|\| (str == ',')) {
	188	if (next != NULL) {
	189	*next = str;
	190	}
	191	return root;
	192	}
	193
	194	/* look for operators */
	195
	196	for (i = 0; i < NB_OPERATORS; i++) {
	197	keyword_t *operator = operators + i;
	198	if (codecmp (operator->keyword, str) == 0) {
	199	VERBOSE (DEBUG, fprintf (stdout, "start processing operator\n"));
	200	if (root) {
	201	if ((prio) && (prio > operator->prio)) {
	202	VERBOSE (DEBUG, fprintf (stdout, "stop because operator priority\n"));
	203	*next = str;
	204	return root;
	205	}
	206	str += operator->offset;
	207	VERBOSE (INFO, fprintf (stdout, "Oper: %d\n", operator->func));
	208	if (subparser (&root, &str, operator->func, operator->nbops, operator->prio) == ERROR_OP) {
	209	delelement (root);
	210	return ERROR_OP;
	211	}
	212	} else if (*str == '-') {
	213	new = newelement (Sig, 1, 9);
	214	if (new == NULL) {
	215	return ERROR_OP;
	216	}
	217	root = new;
	218	} else {
	219	return ERROR_OP;
	220	}
	221	found = 1;
	222	VERBOSE (DEBUG, fprintf (stdout, "stop processing operator\n"));
	223	break;
	224	}
	225	}
	226	if (found) {
	227	continue;
	228	}
	229
	230	/* look for functions */
	231
	232	for (i = 0; i < NB_FUNCTIONS; i++) {
	233	keyword_t *function = functions + i;
	234	if (codecmp (function->keyword, str) == 0) {
	235	VERBOSE (DEBUG, fprintf (stdout, "start processing function\n"));
	236	if (root == NULL) {
	237	VERBOSE (INFO, fprintf (stdout, "Func: %d\n", function->func));
	238	new = newelement (function->func, function->nbops, function->prio);
	239	if (new == NULL) {
	240	return ERROR_OP;
	241	}
	242	root = new;
	243	} else {
	244	delelement (root);
	245	return ERROR_OP;
	246	}
	247	str += function->offset;
	248	found = 1;
	249	VERBOSE (DEBUG, fprintf (stdout, "stop processing function\n"));
	250	break;
	251	}
	252	}
	253	if (found) {
	254	continue;
	255	}
	256
	257	/* look for constant */
	258
	259	for (i = 0; i < NB_CONSTANTS; i++) {
	260	keyword_t *constant = constants + i;
	261	if (codecmp (constant->keyword, str) == 0) {
	262	VERBOSE (DEBUG, fprintf (stdout, "start processing constant\n"));
	263	if (root == NULL) {
	264	VERBOSE (INFO, fprintf (stdout, "Func: %d\n", constant->func));
	265	new = newelement (constant->func, constant->nbops, constant->prio);
	266	if (new == NULL) {
	267	return ERROR_OP;
	268	}
	269	root = new;
	270	} else {
	271	delelement (root);
	272	return ERROR_OP;
	273	}
	274	str += constant->offset;
	275	found = 1;
	276	VERBOSE (DEBUG, fprintf (stdout, "stop processing constant\n"));
	277	break;
	278	}
	279	}
	280	if (found) {
	281	continue;
	282	}
	283
	284	/* look for number */
	285
	286	if (((str >= '0') && (str <= '9')) \|\|
	287	(str == '.') \|\| (str == '+') \|\| (*str == '-')) {
	288	VERBOSE (DEBUG, fprintf (stdout, "start processing value\n"));
	289	char *pt;
	290	double value = strtod (str, &pt);
	291	VERBOSE (INFO, fprintf (stdout, "Value: %f\n", value));
	292	if (str != pt) {
	293	if (root == NULL) {
	294	new = newelement (Val, 1, 5);
	295	if (new == NULL) {
	296	return ERROR_OP;
	297	}
	298	new->value = value;
	299	root = new;
	300	str = pt;
	301	} else if (root->func == Val) {
	302	if ((str == '+') \|\| (str == '-')) {
	303	if ((prio) && (prio > 1)) {
	304	VERBOSE (DEBUG, fprintf (stdout, "stop because operator priority\n"));
	305	*next = str;
	306	return root;
	307	}
	308	if (subparser (&root, &str, Add, 2, 1) == ERROR_OP) {
	309	delelement (root);
	310	return ERROR_OP;
	311	}
	312	} else {
	313	delelement (root);
	314	return ERROR_OP;
	315	}
	316	} else {
	317	delelement (root);
	318	return ERROR_OP;
	319	}
	320	found = 1;
	321	}
	322	VERBOSE (DEBUG, fprintf (stdout, "stop processing value\n"));
	323	}
	324
	325	/* error */
	326
	327	if (!found) {
	328	delelement (root);
	329	return ERROR_OP;
	330	}
	331
	332	}
	333
	334	if (next != NULL) {
	335	*next = str;
	336	}
	337
	338	return root;
	339	}
	340
	341	/* print element tree */
	342
	343	void print_element (element_t *root, int level)
	344	{
	345	char *func = NULL;
	346	int i;
	347
	348	if ((root == NULL) \|\| (root == ERROR_OP)) {
	349	return;
	350	}
	351
	352	for (i = 0; i < level; i++) {
	353	fprintf (stdout, " ");
	354	}
	355
	356	switch (root->func) {
	357	case Val: func = "Value"; break;
	358	case Sig: func = "Sign"; break;
	359	case Add: func = "Addition"; break;
	360	case Sub: func = "Subtraction"; break;
	361	case Mul: func = "Multiplication"; break;
	362	case Div: func = "Division"; break;
	363	case Mod: func = "Modulo"; break;
	364	case Pow: func = "Power"; break;
	365	case Sqr: func = "Square Root"; break;
	366	case Cos: func = "Cosine"; break;
	367	case Sin: func = "Sine"; break;
	368	case Atan: func = "Arc Tangent"; break;
	369	case Log: func = "Logarithm"; break;
	370	case Exp: func = "Exponantial"; break;
	371	case Quit: func = "Quit"; break;
	372	case Help: func = "Help"; break;
	373	case Pi: func = "Pi"; break;
	374	case E: func = "E"; break;
	375	}
	376
	377	fprintf (stdout, "Function: %s\n", func);
	378
	379	if ((root->func == Val) && (root->ops[0] == NULL)) {
	380	for (i = 0; i < level; i++) {
	381	fprintf (stdout, " ");
	382	}
	383	fprintf (stdout, "value: %f\n", root->value);
	384	} else {
	385	for (i = 0; i < root->nbops; i++) {
	386	print_element (root->ops[i], level + 1);
	387	}
	388	}
	389	}
	390
	391	/* quit function */
	392
	393	void quit (void)
	394	{
	395	fprintf (stdout, "bye\n");
	396	exit (0);
	397	}
	398
	399	/* help message */
	400
	401	void help (void)
	402	{
	403	fprintf (stdout, "calc is a simple calculator\n\n");
	404	fprintf (stdout, "supported operators:\n");
	405	fprintf (stdout, " + - * / %% ^\n\n");
	406	fprintf (stdout, "supported functions:\n");
	407	fprintf (stdout, " pow sqrt cos sin atan log exp\n\n");
	408	fprintf (stdout, "miscellaneous functions:\n");
	409	fprintf (stdout, " quit help\n\n");
	410	fprintf (stdout, "supported constants:\n");
	411	fprintf (stdout, " e pi\n");
	412	}
	413
	414	/* evaluate element tree */
	415
	416	#define MASK_SUB 0x1
	417	#define MASK_DIV 0x2
	418
	419	double evaluate_element (element_t *root, char mask)
	420	{
	421	double op0 = 0, op1 = 0;
	422	char nextmask = mask;
	423
	424	if ((root == NULL) \|\| (root == ERROR_OP)) {
	425	VERBOSE (WARNING, fprintf (stdout, "error while evaluating\n"));
	426	return 0;
	427	}
	428
	429	/* mask to manage sub operator sub and div */
	430	switch (root->func) {
	431	case Add:
	432	nextmask &= ~MASK_SUB;
	433	nextmask &= ~MASK_DIV;
	434	break;
	435	case Sub:
	436	nextmask \|= MASK_SUB;
	437	nextmask &= ~MASK_DIV;
	438	break;
	439	case Mul:
	440	nextmask &= ~MASK_DIV;
	441	break;
	442	case Div:
	443	nextmask \|= MASK_DIV;
	444	break;
	445	default:
	446	nextmask = mask;
	447	}
	448
	449	switch (root->func) {
	450	case Val:
	451	case Sig:
	452	op0 = (root->ops[0]) ? evaluate_element (root->ops[0], nextmask) : root->value;
	453	break;
	454	case Add:
	455	case Sub:
	456	case Mul:
	457	case Div:
	458	case Mod:
	459	case Pow:
	460	if (root->ops[1]) {
	461	op1 = evaluate_element (root->ops[1], nextmask);
	462	} else {
	463	VERBOSE (WARNING, fprintf (stdout, "error while evaluating (op[1])\n"));
	464	return 0;
	465	}
	466	/* fallthrough */
	467	case Sqr:
	468	case Cos:
	469	case Sin:
	470	case Atan:
	471	case Log:
	472	case Exp:
	473	if (root->ops[0]) {
	474	op0 = evaluate_element (root->ops[0], 0);
	475	} else {
	476	VERBOSE (WARNING, fprintf (stdout, "error while evaluating (op[0])\n"));
	477	return 0;
	478	}
	479	break;
	480	case Quit:
	481	case Help:
	482	case Pi:
	483	case E:
	484	break;
	485	}
	486
	487	switch (root->func) {
	488	case Val: return op0;
	489	case Sig: return -op0;
	490	case Add: return ((mask & MASK_SUB) == 0) ? op0 + op1 : op0 - op1;
	491	case Sub: return ((mask & MASK_SUB) == 0) ? op0 - op1 : op0 + op1;
	492	case Mul: return ((mask & MASK_DIV) == 0) ? op0 * op1 : op0 / op1;
	493	case Div: return ((mask & MASK_DIV) == 0) ? op0 / op1 : op0 * op1;
	494	case Mod: return fmod (op0, op1);
	495	case Pow: return pow (op0, op1);
	496	case Sqr: return sqrt (op0);
	497	case Cos: return cos (op0);
	498	case Sin: return sin (op0);
	499	case Atan: return atan (op0);
	500	case Log: return log (op0);
	501	case Exp: return exp (op0);
	502	case Quit: quit (); break;
	503	case Help: help (); break;
	504	case Pi: return M_PI;
	505	case E: return M_E;
	506	}
	507
	508	return 0;
	509	}
	510
	511	/* vim: set ts=4 sw=4 et: */