Lexical elements¶
Comments¶
A single line comment can be achieved by using ‘//’.
Encoding¶
Currently, ELI only supports ASCII.
Semicolons¶
A semicolon may have two meanings
- Array dimension delimit. It is a separator used in array indexing. For example,
arr[x;y]; - Multiple statement separator. One line code with multiple statements is supported with semicolons. The execution order of statements is from left to right, but within a statement, the execution order remains the same (from right to left). For example,
a<-!5;[]<-1+a.
Identifiers¶
- An identifier starts with a letter;
- It can follow with arbitrary numbers and underscores(‘_’);
- But, the last character cannot be an underscore
identifier ::= letter { letternum | underscore }
underscore ::= {'_'} letternum
letternum ::= letter | [0-9]
letter ::= [a-zA-Z]
Operators¶
Please refer to the primitive function page.
Integer literals¶
Currently, only decimal integers are supported.
int ::= ['+' | '_'] decimals
decimals ::= digit { digit }
digit ::= [0-9]
Floating-point literals¶
float ::= decimals '.' decimals [exponent] | decimals exponent
exponent ::= ('e' | 'E') ['+' | '_'] decimals
Examples
0. //syntax error
0.1
2.3e5
2.e5 //syntax error
.1e3 //syntax error
String literals¶
A string starts with a single quote('). The content can be any possible ASCII characters. But if you want to include a single quote, you need to type two single quotes consecutively (i.e. '').
string ::= \' { content } \'
content ::= letters | \'\'
letters ::= all ASCII characters except \'
Examples
'It is a nice string'
'It''s a nice string'