expression.y

语法分析 语法分析

%{
{*
   计算简单的数学表达式的yacc程序
   编译：yacc Expression ExpressionY
 *}
unit ExpressionY;

interface
uses
  SysUtils, LexLib, YaccLib, ExpressionL;

%}

%token NAME NUMBER
%%
statement:	NAME '=' expression
	|	expression		{ writeln(format('= %d', [$1])); }
	;

expression:	expression '+' NUMBER	{ $$ := $1 + $3; }
	|	expression '-' NUMBER	{ $$ := $1 - $3; }
	|	NUMBER			{ $$ := $1; }
	;
%%
end.