main

lex.c

@@ -141,7 +141,7 @@ void lex_next(struct lexer *lex) {
 
     if (try_constant(lex, "pi", CONST_PI)) return;
     if (try_constant(lex, "e", CONST_E)) return;
-    if (try_constant(lex, "skibidi", CONST_S)) return;
+    if (try_constant(lex, "skibidi", CONST_S)) return; /* easter egg */
 
     if (try_advance_identifier(lex, lex->variable_name)) {
         lex->tok.type = TOK_VARIABLE;

main.c

@@ -3,17 +3,83 @@
 #include "lex.h"
 #include "parser.h"
 #include "ps_graph.h"
+#include "error_buffer.h"
+
+static void print_usage(FILE *f, const char *name) {
+    fprintf(f, "Usage: %s <function> <output file> [<range>]\n", name);
+    fprintf(f, " <function> ..... The function to plot the graph of.\n");
+    fprintf(f, " <output file> .. Name of the output PostScript file.\n");
+    fprintf(f, " <range> ........ Ranges of the graph in the format of \"xMin:xMax:yMin:yMax\". Optional.\n");
+
+}
+
+static int read_double(const char **str, double *out) {
+    char *end;
+    *out = strtod(*str, &end);
+
+    if (*str == end)
+        return 0;
+
+    *str = end;
+    return 1;
+}
+
+#define EXPECT_DOUBLE(str, out) \
+    if (!read_double(&str, out)) \
+        return 0;
+
+#define EXPECT_CHAR(str, c) \
+    if (*str++ != c) \
+        return 0;
+
+static int parse_range(const char *str, struct graph_range *range) {
+    EXPECT_DOUBLE(str, &range->xmin);
+    EXPECT_CHAR(str, ':');
+    EXPECT_DOUBLE(str, &range->xmax);
+    EXPECT_CHAR(str, ':');
+    EXPECT_DOUBLE(str, &range->ymin);
+    EXPECT_CHAR(str, ':');
+    EXPECT_DOUBLE(str, &range->ymax);
+    EXPECT_CHAR(str, '\0');
+    return 1;
+}
+
+static enum error_code export_to_file(const struct expr_node *node, const struct graph_range *range, const char *out_name) {
+    FILE *file;
+
+    if (!(file = fopen(out_name, "w"))) {
+        fprintf(stderr, "Cannot open \"%s\" for writing!\n", out_name);
+        return ERR_INVALID_FILENAME;
+    }
+    
+    ps_export_graph(file, node, range);
+
+    fclose(file);
+    return ERR_NO_ERR;
+}
 
 int main(int argc, char *argv[]) { 
-
+    enum error_code err;
     struct parser parser;
     struct expr_node *node;
-    FILE *file;
-    struct graph_range graph;
+    struct graph_range range;
 
-    if (argc < 2) {
-        printf("Usage: %s <expression>\n", argv[0]);
-        return 1;
+    if (argc < 3) {
+        print_usage(stderr, argv[0]);
+        return ERR_INVALID_ARGS;
+    }
+
+    if (argc > 3) {
+        if (!parse_range(argv[3], &range)) {
+            fprintf(stderr, "Invalid format of ranges! The correct format is \"xMin:xMax:yMin:yMax\".\n");
+            return ERR_INVALID_ARGS;
+        }
+    }
+    else {
+        range.xmin = -10.0;
+        range.xmax = 10.0;
+        range.ymin = -10.0;
+        range.ymax = 10.0;
     }
 
     node = parser_parse(&parser, argv[1], "x");
@@ -22,23 +88,14 @@ int main(int argc, char *argv[]) {
         fprintf(stderr, "%s", parser_get_error_text(&parser));
         return parser_get_error(&parser);
     }
+    
+    err = export_to_file(node, &range, argv[2]);
 
-    graph.xmin = 0.0;
-    graph.xmax = 6.28;
-    graph.ymin = 0.0;
-    graph.ymax = 2.0;
-    graph.step = 0.001;
-
-    file = fopen("out.ps", "w");
-    ps_export_graph(file, node, &graph);
-    fclose(file);
-
-    file = fopen("graph.dot", "w");
+    /* file = fopen("graph.dot", "w");
     node_debug_print_gv(node, file);
-    fclose(file);
+    fclose(file); */
 
     node_free(node);
 
-
-    return 0;
+    return err;
 }

math_functions.c

@@ -1,10 +1,15 @@
 #include "math_functions.h"
 
 #include <math.h>
+#include <errno.h>
 
 #define MAKE_FUNCTION_1_ARG(name) \
-    static double mf_##name(const double *args) { \
-        return name(args[0]); \
+    static enum eval_result mf_##name(double *y, const double *args) { \
+        errno = 0; \
+        *y = name(args[0]); \
+        if (errno) \
+            return EVAL_ERROR; \
+        return EVAL_OK; \
     }
 
 MAKE_FUNCTION_1_ARG(fabs)
@@ -23,35 +28,51 @@ MAKE_FUNCTION_1_ARG(tanh)
 MAKE_FUNCTION_1_ARG(floor)
 MAKE_FUNCTION_1_ARG(ceil)
 
-static double mf_sgn(const double *args) {
+static double mf_sgn(double *y, const double *args) {
     if (args[0] < 0.0)
-        return -1.0;
+        *y = -1.0;
     else if (args[0] > 0.0)
-        return 1.0;
+        *y = 1.0;
     else
-        return 0.0;
+        *y = 0.0;
+
+    return EVAL_OK;
 }
 
-static double mf_min(const double *args) {
+static double mf_min(double *y, const double *args) {
     if (args[0] < args[1])
-        return args[0];
+        *y = args[0];
+    else
+        *y = args[1];
 
-    return args[1];
+    return EVAL_OK;
 }
 
-static double mf_max(const double *args) {
+static double mf_max(double *y, const double *args) {
     if (args[0] > args[1])
-        return args[0];
+        *y = args[0];
+    else
+        *y = args[1];
 
-    return args[1];
+    return EVAL_OK;
 }
 
-static double mf_mod(const double *args) {
-    return fmod(args[0], args[1]);
+static double mf_mod(double *y, const double *args) {
+    errno = 0;
+    *y = fmod(args[0], args[1]);
+
+    if (errno)
+        return EVAL_ERROR;
+    
+    return EVAL_OK;
 }
 
 const struct math_function *fns_get(void) {
     static const struct math_function fns[] = {
+    /*    +--- název
+          |         +--- počet argumentů
+          |         |   +--- vyhodnocovač
+          |         |   |                   */
         { "abs",    1,  mf_fabs     },
         { "exp",    1,  mf_exp      },
         { "ln",     1,  mf_log      },

math_functions.h

@@ -5,10 +5,18 @@
 
 #define MAX_MATH_FUNCTION_ARGS 2
 
+/**
+ * @brief Výsledek vyhodnocení výrazu
+ */
+enum eval_result {
+    EVAL_OK,
+    EVAL_ERROR
+};
+
 /**
  * @brief Ukazatel na vyhodnocovač matematické funkce
  */
-typedef double (*math_function_ptr)(const double*);
+typedef enum eval_result (*math_function_ptr)(double* y, const double* args);
 
 /**
  * @brief Matematická funkce

ps_graph.c

@@ -1,8 +1,10 @@
 #include "ps_graph.h"
+#include <math.h>
 
 #define GRAPH_SIZE 400
 #define HALF_GRAPH_SIZE (GRAPH_SIZE / 2)
 #define GRID_STEP (GRAPH_SIZE / 10)
+#define FUNCTION_SEGMENTS 1000
 
 void ps_export_graph(FILE *file, const struct expr_node *node, const struct graph_range *range) {
     int i;
@@ -87,12 +89,14 @@ void ps_export_graph(FILE *file, const struct expr_node *node, const struct grap
         "newpath\n"
     );
 
-    for (x = range->xmin; x <= range->xmax; x += range->step) {
+    for (i = 0; i < FUNCTION_SEGMENTS; ++i) {
         const char *cmd = "lineto";
         double xpos, ypos;
-        double y = node_eval(node, x);
+        double y;
        
-        if (y != y) {
+        x = range->xmin + (range->xmax - range->xmin) * (double)i / (double)FUNCTION_SEGMENTS;
+
+        if (node_eval(node, x, &y) != EVAL_OK) {
             first = 1;
             continue;
         }
@@ -105,6 +109,7 @@ void ps_export_graph(FILE *file, const struct expr_node *node, const struct grap
             first = 0;
         }
         fprintf(file, "%.2f %.2f %s\n", xpos, ypos, cmd);
+
     }
 
     fprintf(file,

ps_graph.h

@@ -7,7 +7,6 @@
 struct graph_range {
 	double xmin, xmax;
 	double ymin, ymax;
-	double step;
 };
 
 extern void ps_export_graph(FILE *file, const struct expr_node *node, const struct graph_range *range);

tree.c

@@ -1,6 +1,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <math.h>
+#include <errno.h>
 #include "tree.h"
 
 static struct expr_node *alloc_node(void) {
@@ -255,32 +256,79 @@ void node_debug_print_gv(const struct expr_node *node, FILE *output) {
     fprintf(output, "}\n");
 }
 
+#define INF (1.0e256)
+
+static int is_real(double x) {
+    return x == x && x < INF && x > -INF;
+}
+
+static enum eval_result check_real(double x) {
+    if (is_real(x))
+        return EVAL_OK;
+    else
+        return EVAL_ERROR;
+}
+
+#define RETURN_CHECK_REAL(x) if (is_real((x))) return EVAL_OK; else return EVAL_ERROR;
+
+#define EVAL_CHECK(node, x, y) if (node_eval((node), (x), (y)) != EVAL_OK) return EVAL_ERROR;
+
+enum eval_result node_eval(const struct expr_node *node, double x, double *y) {
+    double tmp1, tmp2;
 
-double node_eval(const struct expr_node *node, double x) {
     switch (node->type) {
         case EXPR_CONST:
-            return node->vals.num;
+            *y = node->vals.num;
+            return check_real(*y);
 
         case EXPR_X:
-            return x;
+            *y = x;
+            return check_real(*y);
 
         case EXPR_NEG:
-            return -node_eval(node->vals.unop, x);
+            EVAL_CHECK(node->vals.unop, x, &tmp1);
+            *y = -tmp1;
+            return EVAL_OK;
 
         case EXPR_ADD:
-            return node_eval(node->vals.binop.left, x) + node_eval(node->vals.binop.right, x);
+            EVAL_CHECK(node->vals.binop.left, x, &tmp1);
+            EVAL_CHECK(node->vals.binop.right, x, &tmp2);
+            *y = tmp1 + tmp2;
+            return check_real(*y);
 
         case EXPR_SUB:
-            return node_eval(node->vals.binop.left, x) - node_eval(node->vals.binop.right, x);
+            EVAL_CHECK(node->vals.binop.left, x, &tmp1);
+            EVAL_CHECK(node->vals.binop.right, x, &tmp2);
+            *y = tmp1 - tmp2;
+            return check_real(*y);
 
         case EXPR_MULT:
-            return node_eval(node->vals.binop.left, x) * node_eval(node->vals.binop.right, x);
+            EVAL_CHECK(node->vals.binop.left, x, &tmp1);
+            EVAL_CHECK(node->vals.binop.right, x, &tmp2);
+            *y = tmp1 * tmp2;
+            return check_real(*y);
 
         case EXPR_DIV:
-            return node_eval(node->vals.binop.left, x) / node_eval(node->vals.binop.right, x);
+            EVAL_CHECK(node->vals.binop.left, x, &tmp1);
+            EVAL_CHECK(node->vals.binop.right, x, &tmp2);
+            
+            if (tmp2 == 0.0)
+                return EVAL_ERROR;
+            
+            *y = tmp1 / tmp2;
+            return check_real(*y);
 
         case EXPR_POW:
-            return pow(node_eval(node->vals.binop.left, x), node_eval(node->vals.binop.right, x));
+            EVAL_CHECK(node->vals.binop.left, x, &tmp1);
+            EVAL_CHECK(node->vals.binop.right, x, &tmp2);
+            
+            errno = 0;
+            *y = pow(tmp1, tmp2);
+            
+            if (errno) 
+                return EVAL_ERROR;
+            
+            return check_real(*y);
 
         case EXPR_FN:
         {
@@ -289,10 +337,10 @@ double node_eval(const struct expr_node *node, double x) {
             const struct math_function *fn = &fns_get()[node->vals.fn.fn_idx];
 
             for (i = 0; i < fn->num_args; ++i) {
-                inner_results[i] = node_eval(node->vals.fn.args[i], x);
+                EVAL_CHECK(node->vals.fn.args[i], x, &inner_results[i]);
             }
 
-            return fn->ptr(inner_results);
+            return fn->ptr(y, inner_results);
         }
     }
 

tree.h

@@ -123,9 +123,10 @@ void node_debug_print_gv(const struct expr_node *node, FILE *output);
  * 
  * @param node Uzel
  * @param x Proměnná
- * @return Hodnota v bodě x
+ * @param y Výsledek vyhodnocení
+ * @return Stav vyhodnocení
  */
-double node_eval(const struct expr_node *node, double x);
+enum eval_result node_eval(const struct expr_node *node, double x, double *y);
 
 /**
  * @brief Uvolní uzel