started work on a lemon sql parser

src/lemon/Makefile

@@ -0,0 +1,11 @@
+
+all: lemon_parser.c flex_lexer.c
+
+lemon_parser.c: lemon_parser.y
+	lemon lemon_parser.y
+
+flex_lexer.c: flex_lexer.l
+	flex --outfile=flex_lexer.c --header-file=flex_lexer.h flex_lexer.l
+
+clean:
+	rm -f lemon_parser.c flex_lexer.c lemon_parser.h flex_lexer.h lemon_parser.out

src/lemon/SQLParser.cpp

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+#include "SQLParser.h"
+#include "lemon_parser.h"
+#include "flex_lexer.h"
+#include <stdio.h>
+
+
+
+void *ParseAlloc(void *(*mallocProc)(size_t));
+void ParseFree(void *p, void (*freeProc)(void*));
+void Parse(void *yyp, int yymajor, const char* text, Statement**);
+
+
+SQLParser::SQLParser() {
+	fprintf(stderr, "SQLParser only has static methods atm! Do not initialize!\n");
+}
+
+
+Statement* SQLParser::parseSQL(const char *text) {
+    yyscan_t scanner;
+    yylex_init(&scanner);
+    
+    // Scan the provided string
+    YY_BUFFER_STATE state = yy_scan_string(text, scanner);
+
+    void* lemonParser = ParseAlloc(malloc);
+    int tokenCode;
+    Statement* result;
+    do {
+        tokenCode = yylex(scanner);
+        Parse(lemonParser, tokenCode, yyget_text(scanner), &result);
+        // printf("Token %d\n", tokenCode);
+    } while (tokenCode > 0);
+
+    yy_delete_buffer(state, scanner);
+    yylex_destroy(scanner);
+    return result;
+}

src/lemon/SQLParser.h

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+#ifndef __SQLPARSER_H_
+#define __SQLPARSER_H_
+
+#include "Statement.h"
+
+class SQLParser {
+public:
+	static Statement* parseSQL(const char* sql);
+
+private:
+	SQLParser();
+};
+
+
+
+#endif

src/lemon/flex_lexer.l

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+%{
+/**
+ * flex_lexer.l file
+ */
+
+#include "lemon_parser.h"
+#include <stdlib.h>
+
+#define TOK(name) { return name; }
+%}
+
+
+%option reentrant
+%option noyywrap
+
+%%
+
+[ \t\n]+	; /* skip whitespace */
+
+SELECT		TOK(SELECT)
+FROM		TOK(FROM)
+GROUP		TOK(GROUP)
+BY			TOK(BY)
+WHERE		TOK(WHERE)
+NOT			TOK(NOT)
+AND			TOK(AND)
+OR			TOK(OR)
+
+"="		|
+"<>" 	|
+"<"		|
+">"		|
+"<="	|
+">="		TOK(COMPARISON)
+
+
+[-+*/(),.;]	TOK(yytext[0])
+
+[0-9]+	|
+[0-9]+"."[0-9]* |
+"."[0-9]*	TOK(INTNUM)
+
+[A-Za-z][A-Za-z0-9_]*	TOK(NAME)
+
+
+'[^'\n]*'	TOK(STRING)
+
+%%
+
+int yyerror(const char *msg) {
+    fprintf(stderr,"Error:%s\n",msg); return 0;
+}

src/lemon/lemon_parser.y

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+%include {
+	#include <assert.h>
+	#include <cstdlib>
+	#include "lib/Statement.h"
+}
+%syntax_error { printf("Lemon syntax error\n"); }
+
+%extra_argument { Statement** result }
+%token_type {const char*}
+%type expr {Statement*}
+
+%left PLUS MINUS .
+
+
+start   ::= prog.
+
+prog    ::= prog print NL .
+prog    ::= prog print .
+prog    ::= .
+
+print   ::= expr(a) .         { *result = a; }
+
+expr(a) ::= NUMBER .                { a = new Statement(eSelect); }
+expr(a) ::= expr(b) PLUS expr .      { a = b; }