dayu的Blog

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其实脚本解释器用像as3或者java这类语言来构建,是比较容易的,由于as3和java都是动态语言,内置了很多支持,外加内存回收和反射的存在.脚本和虚拟机之间几乎是没有任何障碍就可以互掉.性能的损失也可以通过一些手段来避免.

因此,自定义一个自己喜欢,用得舒畅的语言变得很有意思.

dy的关键字很少:var,new,class,function,if,while,break,return,trace

dy的运算符也很少:+,-,*,/,+=,-=,*=,/=,>,==,<,||,&&

dy使用LL(1)的语法,以下是该脚本语言的语法,非常简单:

CLASS ->class IDENT { DecList }
DecList ->varlist
DecList ->funclist
varlist ->var IDENT = EXP ; varlist
funclist ->func funclist
func ->function IDENT ( ParamList ) { stlist }
ParamList ->IDENT ParamRest
ParamRest ->, IDENT
ParamList
stlist ->st stlist
st ->if ( EXP ) { stlist }
st ->while ( EXP ) { stlist }
st ->var IDENT = EXP ;
st ->IDENT Assign EXP ;
st ->EXP ;
EXP ->Term LOP EXP
EXPList ->EXP EXPREST
EXPREST ->, EXP
Term ->facter ROP Term
facter ->gene MOP facter
gene ->IDENT
gene ->NUMBER
gene ->STRING
gene ->IDENT ( EXPList )
gene ->( EXP )
gene ->new IDENT ( )
Assign =
Assign +=
Assign -=
Assign *=
Assign /=
LOP and
LOP or
MOP +
MOP -
MOP *
MOP /
ROP >
ROP <
ROP >=
ROP <=
ROP ==