Lexical Conventions
Since e language was developed based on other programming languages, Most of the syntax is more or less same as other programming language. So if you know lexical conventions of C++ or C, then you can follow e language without any problem.

File Structures

e files should have .e as extension.
Example

• memory.e
• hello.e
  When the code size is big, it is better to have code organized into multiple files. This is same as any programming language.When importing other file in C++ or C language we use #include, in e language we use import filename, below example shows how it is done.

1 <'

 2

 3 import hello_world.e;

 4 import memory;

 5

 6 // Rest of the code

 7

 8

 9 '>
As you see, first file has .e extension and second file does not. Well in e language, we don't need to specify the extension of e file, the compiler assumes .e as extension.

Within file, we can have code segments. Beginning of code segment is marked with <' and end of code segment is marked with '> . And code that does not fall within this code segments are treated as comments

  1 // Anything here is comment

  2 <'

  3 //Code here

  4 

  5 

  6 

  7 '>

  8 

  9 //This is also comment

 10 

 11 <'

 12 //Code continue

 13 

 14 '>

White Spaces and Comments

As of comments, in e language, we can comment code in three ways

• // : This is same as in Verilog and C language
• -- : This is same as in VHDL language
• : This is block comment, any text that falls outside is treated as comment.

·         1 <'

·         2 -- Single line comment

·         3 // This is also single line comment

·         4

·         5 //Code here

·         6

·         7 '>

·         8 Multipe line comment

·         9 So ignored

·        10

·        11 <'

·        12 //Code continue..

·        13

·        14 '>

Literals and Constants

• Literals are numeric, character and string values. Following literals and constants are in e language. Unsized Numbers: As name implies, they are unsized, can be both positive and negative
  • Hexadecimal numbers start with 0x
  • Binary numbers start with 0b
  • Octal number start with 0o
  • Example : 32, 44, 0x20, 0b101010101, 0o11_11, 0xDEAD_BEEF, -1, -0x44
  • Kilo or Muliple of 1024 : 1K, 10K
  • Mega or 1024*1024 : 1M, 10M
• Sized Numbers:
  • Hexadecimal numbers start with 'h
  • Binary numbers start with 'b
  • Decimal numbers start with 'd
  • Octal number start with 'o
  • If the value number is more than the specified size in bits, its most significant bits are ignored.
  • If the value number is less that the specified size, it is padded by zeros.
  • Example : 16'd32, 32'd44, 8'h20, 8'b0101_0101, 12'o1111, 32'hDEAD_BEEF, -4'h1
• Predefined Constants: There are few list of pre defined constants a below.
  • TRUE For Boolean variables and expressions.
  • FALSE For Boolean variables and expressions.
  • NULL For structs, specifies a NULL pointer.
  • NULL For structs, specifies a NULL pointer.
  • MAX_INT Represents the largest 32-bit int (2^31 -1)
  • MAX_INT Represents the largest 32-bit int (2^31 -1)
  • MAX_UINT Represents the largest 32-bit uint (2^32 -1).
• Literal String:A literal string is a sequence of zero or more ASCII characters enclosed by double quotes (" ").
  • Example : "This is sample string"
  • Example : "" -Empty string
  • Escape sequence in e is same as in any other programming lanuage \n, \t, \\ etc
• Literal Character: We really don't care about this type

·         1

·         2 <'

·         3 // Example of numeric values

·         4 struct abc {

·         5 data : int ;

·         6

·         7   my_method () is {

·         8    // Unsigned numbers

·         9    data = 0x1; // Hexadecimal

·        10    data = 33;  // Decimal

·        11    data = 0b11111_00000;//Binary

·        12    data = 0o777_333; // Octal

·        13    // Signed numbers

·        14    data = 32'hDEAD_BEAF; // 32 bit Hexadecimal

·        15    data = 8'd33; // 8 bit decimal

·        16    data = 9'b1111_0000; // 8 bit binary

·        17    data = 18'o777_333; // 18 bit Octal

·        18    // Kilo and Mega

·        19    data = 1K; // 1024

·        20    data = 5M; // 1024*1024*5

·        21   };

·        22

·        23 };

·        24 '>

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