Add basic lexer and parser

lexer.l

@@ -0,0 +1,38 @@
+%{
+
+#include <stdio.h>
+#include "expression.h"
+#include "parser.tab.h"
+
+%}
+
+%%
+
+"\n"	{ return WEBDICE_TOKEN_EOL; }
+-?[0-9]+	{
+		int64_t aux;
+
+		sscanf(yytext,"%ld",&aux);
+		yylval.exp.constant.id = WEBDICE_CONST;
+		yylval.exp.constant.value = aux;
+		return WEBDICE_TOKEN_CONST;
+	}
+-?[0-9]+d[0-9]+	{
+		int64_t count,type;
+
+		sscanf(yytext,"%ldd%ld",&count,&type);
+		yylval.exp.roll.id = WEBDICE_ROLL;
+		yylval.exp.roll.count = count;
+		yylval.exp.roll.type = type;
+		return WEBDICE_TOKEN_ROLL;
+	}
+"("	{ return WEBDICE_TOKEN_LPAREN; }
+")"	{ return WEBDICE_TOKEN_RPAREN; }
+"*"	{ return WEBDICE_TOKEN_MUL; }
+"/"	{ return WEBDICE_TOKEN_DIV; }
+"+"	{ return WEBDICE_TOKEN_ADD; }
+"-"	{ return WEBDICE_TOKEN_SUB; }
+[ \t]+	{}
+.	{ fprintf(stderr,"%s",yytext); return WEBDICE_TOKEN_EOL; }
+
+%%

parser.y

@@ -0,0 +1,45 @@
+%{
+#include "expression.h"
+
+int yylex();
+int yyerror(char*);
+
+%}
+
+%parse-param {union expression** root};
+
+%union {
+	union expression* exp;
+}
+
+%token WEBDICE_TOKEN_EOL
+%token <exp> WEBDICE_TOKEN_CONST
+%token <exp> WEBDICE_TOKEN_ROLL
+%token WEBDICE_TOKEN_LPAREN
+%token WEBDICE_TOKEN_RPAREN
+
+%left WEBDICE_TOKEN_ADD
+%left WEBDICE_TOKEN_SUB
+%left WEBDICE_TOKEN_MUL
+%left WEBDICE_TOKEN_DIV
+
+%type <exp> expression
+
+%start lines
+
+%%
+expression:	expression WEBDICE_TOKEN_ADD expression	{ $$ = webdice_add($1,$3); }
+	|	expression WEBDICE_TOKEN_SUB expression	{ $$ = webdice_sub($1,$3); }
+	|	expression WEBDICE_TOKEN_MUL expression	{ $$ = webdice_mul($1,$3); }
+	|	expression WEBDICE_TOKEN_DIV expression	{ $$ = webdice_div($1,$3); }
+	|	WEBDICE_TOKEN_CONST	{ $$ = $1; }
+	|	WEBDICE_TOKEN_ROLL	{ $$ = $1; }
+	|	WEBDICE_TOKEN_LPAREN expression WEBDICE_TOKEN_RPAREN	{ $$ = $2; }
+	;
+
+lines:
+	|	lines WEBDICE_TOKEN_EOL	{ (*root) = NULL; }
+	|	lines expression WEBDICE_TOKEN_EOL	{ (*root) = $2; }
+	;
+
+%%