词法分析器的输出是什么,该如何解决
词法分析器的输出是什么
一般是保存为什么形式的
------解决方案--------------------
C++ Tokens
A token is the smallest element of a C++ program that is meaningful to the compiler. The C++ parser recognizes these kinds of tokens: identifiers, keywords, literals, operators, punctuators, and other separators. A stream of these tokens makes up a translation unit.
Tokens are usually separated by “white space.” White space can be one or more:
Blanks
Horizontal or vertical tabs
New lines
Formfeeds
Comments
Syntax
token :
keyword
identifier
constant
operator
punctuator
preprocessing-token :
header-name
identifier
pp-number
character-constant
string-literal
operator
punctuator
each nonwhite-space character that cannot be one of the above
The parser separates tokens from the input stream by creating the longest token possible using the input characters in a left-to-right scan. Consider this code fragment:
a = i+++j;
The programmer who wrote the code might have intended either of these two statements:
a = i + (++j)
a = (i++) + j
Because the parser creates the longest token possible from the input stream, it chooses the second interpretation, making the tokens i++, +, and j.
------解决方案--------------------
lex&yacc时常用的表达式解析组合。
用lex编辑源代码，将源代码存储为a.l，然后用进行编译，输入flex a.l，编译后生成lex.yy.c(yy 指的是yacc)文件，用c编译器打开（确保example.txt存储在相同目录下），编译运行即可.
输出形式是token：<单词种别，单词符号的属性值>
参考：http://blog.****.net/xn4545945/article/details/8273499
一般是保存为什么形式的
------解决方案--------------------
C++ Tokens
A token is the smallest element of a C++ program that is meaningful to the compiler. The C++ parser recognizes these kinds of tokens: identifiers, keywords, literals, operators, punctuators, and other separators. A stream of these tokens makes up a translation unit.
Tokens are usually separated by “white space.” White space can be one or more:
Blanks
Horizontal or vertical tabs
New lines
Formfeeds
Comments
Syntax
token :
keyword
identifier
constant
operator
punctuator
preprocessing-token :
header-name
identifier
pp-number
character-constant
string-literal
operator
punctuator
each nonwhite-space character that cannot be one of the above
The parser separates tokens from the input stream by creating the longest token possible using the input characters in a left-to-right scan. Consider this code fragment:
a = i+++j;
The programmer who wrote the code might have intended either of these two statements:
a = i + (++j)
a = (i++) + j
Because the parser creates the longest token possible from the input stream, it chooses the second interpretation, making the tokens i++, +, and j.
------解决方案--------------------
lex&yacc时常用的表达式解析组合。
用lex编辑源代码，将源代码存储为a.l，然后用进行编译，输入flex a.l，编译后生成lex.yy.c(yy 指的是yacc)文件，用c编译器打开（确保example.txt存储在相同目录下），编译运行即可.
输出形式是token：<单词种别，单词符号的属性值>
参考：http://blog.****.net/xn4545945/article/details/8273499