commit 77b95df534de20c182a14c667fa08512c310a913
Author: Alex Kotov <kotovalexarian@gmail.com>
Date:   Wed May 3 22:42:26 2023 +0400

    lexer

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..b54616a
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+/*.o
+
+/lisp
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..ee3e1f3
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,12 @@
+all: lisp
+
+CC = gcc
+CFLAGS = -Wall -Wextra
+
+OBJS = main.c.o
+
+lisp: $(OBJS)
+	$(CC) -o $@ $^ $(CFLAGS)
+
+%.c.o: %.c
+	$(CC) -c $< -o $@ $(CFLAGS)
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..28ada25
--- /dev/null
+++ b/main.c
@@ -0,0 +1,217 @@
+#include <assert.h>
+#include <ctype.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+enum State {
+    STATE_INIT,
+    STATE_WHITESPACE,
+    STATE_OPEN,
+    STATE_CLOSE,
+    STATE_ID,
+};
+
+struct Token {
+    struct Token *next;
+    enum State type;
+    char *val;
+};
+
+static char buffer[1024];
+static size_t buffer_index = 0;
+
+static enum State state = STATE_INIT;
+static struct Token *tokens = NULL;
+
+static void error(const char *msg);
+static const char *state_str(enum State state);
+static void buffer_add(char chr);
+static void buffer_clean();
+static void token_add(enum State type, char *val);
+static void lex(char chr);
+
+int main()
+{
+    char chr;
+    while ((chr = getchar()) != EOF) {
+        lex(chr);
+    }
+
+    printf("Tokens:\n");
+
+    for (const struct Token *token = tokens; token; token = token->next) {
+        printf("%s:%s;\n", state_str(token->type), token->val);
+    }
+
+    exit(EXIT_SUCCESS);
+}
+
+void error(const char *msg)
+{
+    printf("ERROR: %s\n", msg);
+    exit(EXIT_FAILURE);
+}
+
+const char *state_str(enum State state)
+{
+    switch (state) {
+    case STATE_INIT: return "STATE_INIT";
+    case STATE_WHITESPACE: return "STATE_WHITESPACE";
+    case STATE_OPEN: return "STATE_OPEN";
+    case STATE_CLOSE: return "STATE_CLOSE";
+    case STATE_ID: return "STATE_ID";
+    }
+    return NULL;
+}
+
+void buffer_add(char chr)
+{
+    if (buffer_index >= 1000) error("token too long");
+    buffer[buffer_index++] = chr;
+    buffer[buffer_index] = 0;
+}
+
+void buffer_clean()
+{
+    buffer_index = 0;
+}
+
+void token_add(enum State type, char *val)
+{
+    struct Token *token = malloc(sizeof(struct Token));
+    assert(token);
+    token->next = NULL;
+    token->type = type;
+    token->val = malloc(strlen(val) + 1);
+    assert(token->val);
+    strcpy(token->val, val);
+
+    if (!tokens) {
+        tokens = token;
+    } else {
+        for (struct Token *curr = tokens; curr; curr = curr->next) {
+            if (!curr->next) {
+                curr->next = token;
+                break;
+            }
+        }
+    }
+}
+
+void lex(char chr)
+{
+    switch (state) {
+    case STATE_INIT:
+        if (chr == '(') {
+            state = STATE_OPEN;
+            buffer_add(chr);
+        } else if (chr == ')') {
+            state = STATE_CLOSE;
+            buffer_add(chr);
+        } else if (isspace(chr)) {
+            state = STATE_WHITESPACE;
+            buffer_add(chr);
+        } else if (isalpha(chr)) {
+            state = STATE_ID;
+            buffer_add(chr);
+        } else {
+            error("invalid char (STATE_INIT)");
+        }
+        break;
+    case STATE_WHITESPACE:
+        if (chr == '(') {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_OPEN;
+            buffer_add(chr);
+        } else if (chr == ')') {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_CLOSE;
+            buffer_add(chr);
+        } else if (isspace(chr)) {
+            buffer_add(chr);
+        } else if (isalpha(chr)) {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_ID;
+            buffer[buffer_index++] = chr;
+        } else {
+            error("invalid char (STATE_WHITESPACE)");
+        }
+        break;
+    case STATE_OPEN:
+        if (chr == '(') {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_OPEN;
+            buffer_add(chr);
+        } else if (chr == ')') {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_CLOSE;
+            buffer_add(chr);
+        } else if (isspace(chr)) {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_WHITESPACE;
+            buffer_add(chr);
+        } else if (isalpha(chr)) {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_ID;
+            buffer_add(chr);
+        } else {
+            error("invalid char (STATE_OPEN)");
+        }
+        break;
+    case STATE_CLOSE:
+        if (chr == '(') {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_OPEN;
+            buffer_add(chr);
+        } else if (chr == ')') {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_CLOSE;
+            buffer_add(chr);
+        } else if (isspace(chr)) {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_WHITESPACE;
+            buffer_add(chr);
+        } else if (isalpha(chr)) {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_ID;
+            buffer_add(chr);
+        } else {
+            error("invalid char (STATE_CLOSE)");
+        }
+        break;
+    case STATE_ID:
+        if (chr == '(') {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_OPEN;
+            buffer_add(chr);
+        } else if (chr == ')') {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_CLOSE;
+            buffer_add(chr);
+        } else if (isspace(chr)) {
+            token_add(state, buffer);
+            buffer_clean();
+            state = STATE_WHITESPACE;
+            buffer_add(chr);
+        } else if (isalnum(chr)) {
+            buffer_add(chr);
+        } else {
+            error("invalid char (STATE_ID)");
+        }
+    }
+}