Data commit

Task/Truth-table/C/truth-table.c

@@ -0,0 +1,193 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#define TRUE 1
+#define FALSE 0
+#define STACK_SIZE 80
+#define BUFFER_SIZE 100
+
+typedef int bool;
+
+typedef struct {
+    char name;
+    bool val;
+} var;
+
+typedef struct {
+    int top;
+    bool els[STACK_SIZE];
+} stack_of_bool;
+
+char expr[BUFFER_SIZE];
+int expr_len;
+var vars[24];
+int vars_len;
+
+/* stack manipulation functions */
+
+bool is_full(stack_of_bool *sp) {
+    return sp->top == STACK_SIZE - 1;
+}
+
+bool is_empty(stack_of_bool *sp) {
+    return sp->top == -1;
+}
+
+bool peek(stack_of_bool *sp) {
+    if (!is_empty(sp))
+        return sp->els[sp->top];
+    else {
+        printf("Stack is empty.\n");
+        exit(1);
+    }
+}
+
+void push(stack_of_bool *sp, bool val) {
+    if (!is_full(sp)) {
+        sp->els[++(sp->top)] = val;
+    }
+    else {
+        printf("Stack is full.\n");
+        exit(1);
+    }
+}
+
+bool pop(stack_of_bool *sp) {
+    if (!is_empty(sp))
+        return sp->els[(sp->top)--];
+    else {
+        printf("\nStack is empty.\n");
+        exit(1);
+    }
+}
+
+void make_empty(stack_of_bool *sp) {
+    sp->top = -1;
+}
+
+int elems_count(stack_of_bool *sp) {
+    return (sp->top) + 1;
+}
+
+bool is_operator(const char c) {
+   return c == '&' || c == '|' || c == '!' || c == '^';
+}
+
+int vars_index(const char c) {
+   int i;
+   for (i = 0; i < vars_len; ++i) {
+       if (vars[i].name == c) return i;
+   }
+   return -1;
+}
+
+bool eval_expr() {
+    int i, vi;
+    char e;
+    stack_of_bool s;
+    stack_of_bool *sp = &s;
+    make_empty(sp);
+    for (i = 0; i < expr_len; ++i) {
+        e = expr[i];
+        if (e == 'T')
+            push(sp, TRUE);
+        else if (e == 'F')
+            push(sp, FALSE);
+        else if((vi = vars_index(e)) >= 0) {
+            push(sp, vars[vi].val);
+        }
+        else switch(e) {
+            case '&':
+                push(sp, pop(sp) & pop(sp));
+                break;
+            case '|':
+                push(sp, pop(sp) | pop(sp));
+                break;
+            case '!':
+                push(sp, !pop(sp));
+                break;
+            case '^':
+                push(sp, pop(sp) ^ pop(sp));
+                break;
+            default:
+                printf("\nNon-conformant character '%c' in expression.\n", e);
+                exit(1);
+        }
+    }
+    if (elems_count(sp) != 1) {
+        printf("\nStack should contain exactly one element.\n");
+        exit(1);
+    }
+    return peek(sp);
+}
+
+void set_vars(int pos) {
+    int i;
+    if (pos > vars_len) {
+        printf("\nArgument to set_vars can't be greater than the number of variables.\n");
+        exit(1);
+    }
+    else if (pos == vars_len) {
+        for (i = 0; i < vars_len; ++i) {
+            printf((vars[i].val) ? "T  " : "F  ");
+        }
+        printf("%c\n", (eval_expr()) ? 'T' : 'F');
+    }
+    else {
+        vars[pos].val = FALSE;
+        set_vars(pos + 1);
+        vars[pos].val = TRUE;
+        set_vars(pos + 1);
+    }
+}
+
+/* removes whitespace and converts to upper case */
+void process_expr() {
+    int i, count = 0;
+    for (i = 0; expr[i]; ++i) {
+        if (!isspace(expr[i])) expr[count++] = toupper(expr[i]);
+    }
+    expr[count] = '\0';
+}
+
+int main() {
+    int i, h;
+    char e;
+    printf("Accepts single-character variables (except for 'T' and 'F',\n");
+    printf("which specify explicit true or false values), postfix, with\n");
+    printf("&|!^ for and, or, not, xor, respectively; optionally\n");
+    printf("seperated by whitespace. Just enter nothing to quit.\n");
+
+    while (TRUE) {
+        printf("\nBoolean expression: ");
+        fgets(expr, BUFFER_SIZE, stdin);
+        fflush(stdin);
+        process_expr();
+        expr_len = strlen(expr);
+        if (expr_len == 0) break;
+        vars_len = 0;
+        for (i = 0; i < expr_len; ++i) {
+            e = expr[i];
+            if (!is_operator(e) && e != 'T' && e != 'F' && vars_index(e) == -1) {
+                vars[vars_len].name = e;
+                vars[vars_len].val = FALSE;
+                vars_len++;
+            }
+        }
+        printf("\n");
+        if (vars_len == 0) {
+            printf("No variables were entered.\n");
+        }
+        else {
+            for (i = 0; i < vars_len; ++i)
+                printf("%c  ", vars[i].name);
+            printf("%s\n", expr);
+            h = vars_len * 3 + expr_len;
+            for (i = 0; i < h; ++i) printf("=");
+            printf("\n");
+            set_vars(0);
+        }
+    }
+    return 0;
+}