语法
官方文档：https://www.elastic.co/guide/en/elasticsearch/painless/current/index.html
字面量
整数
包括十进制、八进制、十六进制
l 代表 long, f 代表float, d 代表 double ,默认是int
INTEGER: '-'? ( '0' | [1-9] [0-9]* ) [lLfFdD]?;
OCTAL: '-'? '0' [0-7]+ [lL]?;
HEX: '-'? '0' [xX] [0-9a-fA-F]+ [lL]?;
0 // integer literal of 0
0D // double literal of 0.0
1234L // long literal of 1234
-90F // float literal of -90.0
-022 // integer literal of -18 specified in octal
0xF2A // integer literal of 3882
浮点数
f 代表 float 代表 d 代表 double 默认是 double
DECIMAL: '-'? ( '0' | [1-9] [0-9]* ) (DOT [0-9]+)? ( [eE] [+\-]? [0-9]+ )? [fFdD]?;
0.0 // double value of 0.0
1E6 // double value of 1000000
0.977777 // double value of 0.97777
-126.34 // double value of -126.34
89.9F // float value of 89.9
字符串
可以使用单引号或者双引号
STRING: ( '"' ( '\\"' | '\\\\' | ~[\\"] )*? '"' ) | ( '\'' ( '\\\'' | '\\\\' | ~[\\'] )*? '\'' );
"double-quoted String literal"
'single-quoted String literal'
"\"double-quoted String with escaped double-quotes\" and backslash: \\"
'\'single-quoted String with escaped single-quotes\' and backslash \\'
"double-quoted String with non-escaped 'single-quotes'"
'single-quoted String with non-escaped "double-quotes"'
字符
无法直接定义一个char，必须通过强制转换，如果强制转换多个字符的字符串，将会抛出异常
(char)"C"
(char)'c'
变量
变量名
变量名必须以字母或下划线开始。不能使用关键字或类型作为标识符。
ID: [_a-zA-Z] [_a-zA-Z-0-9]*;
_
a
Z
id
list
list0
MAP25
_map25
变量申明
使用之前必须先申明 type-name identifier-name
declaration : type ID assignment? (',' ID assignment?)*;
type: ID ('.' ID)* ('[' ']')*;
assignment: '=' expression;
int x; // Declare a variable with type int and id x
List y; // Declare a variable with type List and id y
int x, y, z; // Declare variables with type int and ids x, y, and z
int x, y = 5, z; //Declare int x; store default int 0 to x; declare int y; store int 5 to y; declare int z; store default int 0 to z;
def[] d; // Declare the variable d with type def[]
Map[][] m; //Declare Map[][] m; store default null to m
int i = 10; // Declare the int variable i and set it to the int literal 10
变量赋值
基本跟其他语言一致
assignment: ID '=' expression
int i; // Declare an int i
i = 10; // Set the int i to the int literal 10
int i = 10; // Declare the int variable i and set it the int literal 1
double j = 2.0; // Declare the double variable j and set it to the double literal 2.0
int i = 10; // Declare the int variable i and set it to the int literal 10
int j = i; // Declare the int variable j and set it to the int variable i
ArrayList l = new ArrayList(); // Declare an ArrayList variable l and set it to a newly allocated ArrayList
Map m = new HashMap(); // Declare a Map variable m and set it to a newly allocated HashMap
List l = new ArrayList(); // Declare List variable l and set it a newly allocated ArrayList
List k = l; // Declare List variable k and set it to the value of the List variable l
List m; // Declare List variable m and set it the default value null
m = k; // Set the value of List variable m to the value of List variable k
int[] ia1; //Declare int[] ia1; store default null to ia1
ia1 = new int[2]; //Allocate 1-d int array instance with length [2] → 1-d int array reference; store 1-d int array reference to ia1
ia1[0] = 1; //Load from ia1 → 1-d int array reference; store int 1 to index [0] of 1-d int array reference
int[] ib1 = ia1; //Declare int[] ib1; load from ia1 → 1-d int array reference; store 1-d int array reference to ib1; (note ia1 and ib1 refer to the same instance known as a shallow copy)
int[][] ic2 = new int[2][5]; //Declare int[][] ic2; allocate 2-d int array instance with length [2, 5] → 2-d int array reference; store 2-d int array reference to ic2
ic2[1][3] = 2; //Load from ic2 → 2-d int array reference; store int 2 to index [1, 3] of 2-d int array reference
ic2[0] = ia1; //Load from ia1 → 1-d int array reference; load from ic2 → 2-d int array reference; store 1-d int array reference to index [0] of 2-d int array reference; (note ia1, ib1, and index [0] of ia2 refer to the same instance)