commit 652d7cd7f085580d451692526c646fcd2d658aa4
Author: Ilya Bezrukov <bezrukoff888@gmail.com>
Date:   Tue Oct 15 20:35:50 2024 +0300

    Initial

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..d4e23c5
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,35 @@
+CC := gcc
+CFLAGS := -Wall
+LDFLAGS :=
+INCLUDE := -I include
+
+EXENAME := nrr
+
+OBJ := obj
+BIN := bin
+
+SOURCES := main.c
+OBJECTS := $(addprefix $(OBJ)/, $(SOURCES:.c=.o))
+TARGET := $(BIN)/$(EXENAME)
+
+all: $(TARGET)
+
+run: $(TARGET)
+	@./$(TARGET)
+
+$(TARGET): $(OBJECTS) | $(BIN)
+	$(CC) $(CFLAGS) $(INCLUDE) $(OBJECTS) -o $(TARGET) $(LDFLAGS)
+
+$(OBJ)/%.o: %.c | $(OBJ)
+	$(CC) $(CFLAGS) $(INCLUDE) -c $< -o $@
+
+$(BIN):
+	@mkdir -p $(BIN)
+
+$(OBJ):
+	@mkdir -p $(OBJ)
+
+clean:
+	@rm -rf $(BIN) $(OBJ)
+
+.PHONY: all clean run
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..0655a91
--- /dev/null
+++ b/main.c
@@ -0,0 +1,213 @@
+/*
+
+E ::= UT{+T}{-T}
+T ::= F{*F}{/F}
+F ::= (E)|i
+U ::= -|+|_
+
+'_' stands for empty sequence 
+
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+
+
+#define fatal(...) {\
+        fprintf(stderr, "\nError at char %d\n", number);\
+        fprintf(stderr, "%s\n", line);\
+        for (int i = 0; i < number - 1; i++)\
+            fputc(' ', stderr);\
+        fprintf(stderr, "^\nMessage: ");\
+        fprintf(stderr, __VA_ARGS__);\
+        exit(1);\
+    }
+
+
+typedef enum _NodeType {
+    NNUM = 1,
+    NOP = 2
+} NodeType;
+
+typedef struct _Node Node;
+struct _Node {
+    Node *parent;
+    Node *left;
+    Node *right;
+
+    NodeType type;
+
+    int number;
+    char operator;  // + - * / m p
+};
+
+Node *e();
+Node *t();
+Node *f();
+Node *u();
+
+char line[1024];
+int symbol;
+int number = 0;
+void scan();
+
+int LRN(Node *node);
+
+
+int main(int argc, char* argv[]) {
+
+    memset(line, 0, 1024);
+
+    scan();
+    Node *root = e();
+
+    if (symbol != '\n') {
+        fatal("Syntax invalid\n");
+    }
+
+    printf("Success\n");
+    printf("Answer: %d\n", LRN(root));
+
+    return 0;
+}
+
+void scan() {
+    symbol = getchar();
+    if (symbol == '\n')
+        line[number++] = ' ';
+    else
+        line[number++] = symbol;
+}
+
+Node *e() {
+    Node *left, *right, *root;
+
+    root = u();
+    left = t();
+
+    if (root != NULL) {
+        root->left = left;
+        left = root;
+    }
+
+    while (symbol == '+' || symbol == '-') {
+        root = calloc(sizeof(Node), 1);
+        root->type = NOP;
+        root->operator = symbol;
+
+        scan();
+        right = t();
+
+        root->left = left;
+        root->right = right;
+
+        left->parent = root;
+        right->parent = root;
+        left = root;
+        right = NULL;
+    }
+    return root;
+}
+
+Node *t() {
+    Node *left, *right, *root;
+    root = left = f();
+
+    while (symbol == '*' || symbol == '/') {
+        root = calloc(sizeof(Node), 1);
+        root->type = NOP;
+        root->operator = symbol;
+
+        scan();
+        right = f();
+        
+        root->left = left;
+        root->right = right;
+
+        left->parent = root;
+        right->parent = root;
+        left = root;
+        right = NULL;
+    }
+    return root;
+}
+
+Node *f() {
+    Node *node;
+    if (symbol == '(') {
+        scan();
+        node = e();
+        if (symbol != ')') {
+            fatal("Expected parentheses, found '%c'\n", symbol);
+        }
+    }
+    else if (symbol < '0' || symbol > '9') {
+        if (symbol == '\n') {
+            fatal("LF too early\n");
+        }
+        else {
+            fatal("Unexpected symbol '%c'\n", symbol);
+        }
+    }
+    else {
+        node = calloc(sizeof(Node), 1);
+        node->type = NNUM;
+        node->number = (int) (symbol - '0'); 
+    }
+    scan();
+    return node;
+}
+
+Node *u() {
+    if (symbol == '-' || symbol == '+') {
+        Node *node = calloc(sizeof(Node), 1);
+        node->type = NOP;
+        node->operator = (symbol == '+') ? 'p' : 'm';
+        scan();
+        return node;
+    }
+    return NULL;
+}
+
+int LRN(Node *node) {
+    int l, r, answer;
+
+    if (node == NULL)
+        return 0;
+
+    if (node->left != NULL)
+        l = LRN(node->left);
+
+    if (node->right != NULL)
+        r = LRN(node->right);
+
+    if (node->type == NOP) {
+        switch (node->operator) {
+        case '+':
+            answer = l + r; break;
+        case '-':
+            answer = l - r; break;
+        case '*':
+            answer = l * r; break;
+        case '/':
+            answer = l / r; break;
+        case 'm':
+            answer = -l; break;
+        case 'p':
+            answer = +l; break;
+        default:
+            fatal("Invalid operator indentifier: '%c'\n", node->operator); break;
+        }
+    }
+    else if (node->type == NNUM) {
+        answer = node->number;
+    }
+    else {
+        answer = 0;
+    }
+
+    free(node);
+    return answer;
+}