Add a sample of simple JSON parser

sample/json.y

@@ -0,0 +1,136 @@
+/*
+ * Simple JSON parser
+ *
+ * $ lrama -d json.y -o json.c && gcc -Wall json.c -o json && ./json <<< '{"foo": 42, "bar": [1, 2, 3], "baz": {"qux": true}}'
+ * JSON parsed successfully!
+ * $ lrama -d json.y -o json.c && gcc -Wall json.c -o json && ./json <<< '{"foo": invalid }'
+ * Unexpected literal: invalid
+ */
+
+%{
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <string.h>
+%}
+
+%code provides {
+    static int yylex(YYSTYPE *lval, YYLTYPE *loc);
+    static int yyerror(YYLTYPE *loc, const char *s);
+}
+
+%union {
+    char *str;
+    double num;
+}
+
+%token STRING NUMBER TRUE FALSE NULL_T
+
+%locations
+
+%%
+
+json: object
+    | array
+    ;
+
+object: '{' members? '}'
+      ;
+
+members: separated_nonempty_list(',', pair)
+       ;
+
+pair: STRING ':' value
+    ;
+
+array: '[' elements? ']'
+     ;
+
+elements: separated_nonempty_list(',', value)
+        ;
+
+value: STRING | NUMBER | object | array | TRUE | FALSE | NULL_T;
+
+%%
+
+static int yylex(YYSTYPE *yylval, YYLTYPE *loc) {
+    int c;
+    while ((c = getchar()) != EOF && isspace(c));
+    if (c == EOF) return 0;
+    if (c == '{' || c == '}' || c == '[' || c == ']' || c == ':' || c == ',') {
+        return c;
+    }
+    if (c == '"') {
+        char buffer[1024];
+        int i = 0;
+        while ((c = getchar()) != EOF && c != '"') {
+            if (c == '\\') {
+                int next = getchar();
+                if (next == EOF)
+                    break;
+                buffer[i++] = next;
+            } else {
+                buffer[i++] = c;
+            }
+            if (i >= 1023)
+                break;
+        }
+        buffer[i] = '\0';
+        yylval->str = strdup(buffer);
+        return STRING;
+    }
+
+    if (c == '-' || isdigit(c)) {
+        char num_buffer[64];
+        int i = 0;
+        num_buffer[i++] = c;
+        while ((c = getchar()) != EOF && (isdigit(c) || c == '.')) {
+            num_buffer[i++] = c;
+            if (i >= 63)
+                break;
+        }
+        num_buffer[i] = '\0';
+        if (c != EOF)
+            ungetc(c, stdin);
+        yylval->num = atof(num_buffer);
+        return NUMBER;
+    }
+
+    if (isalpha(c)) {
+        char word[16];
+        int i = 0;
+        word[i++] = c;
+        while ((c = getchar()) != EOF && isalpha(c)) {
+            word[i++] = c;
+            if (i >= 15)
+                break;
+        }
+        word[i] = '\0';
+        if (c != EOF)
+            ungetc(c, stdin);
+        if (strcmp(word, "true") == 0)
+            return TRUE;
+        else if (strcmp(word, "false") == 0)
+            return FALSE;
+        else if (strcmp(word, "null") == 0)
+            return NULL_T;
+        else {
+            fprintf(stderr, "Unexpected literal: %s\n", word);
+            exit(1);
+        }
+    }
+
+    fprintf(stderr, "Unexpected character: %c\n", c);
+    return 0;
+}
+
+static int yyerror(YYLTYPE *loc, const char *s) {
+    fprintf(stderr, "Error: %s\n", s);
+    return 0;
+}
+
+int main() {
+    yyparse();
+    printf("JSON parsed successfully!\n");
+    return 0;
+}