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.

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 are same as in any programming languages, you can refer to Verilog tutorial section if you need to know more on this.

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 <' and '> 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 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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Deepak Kumar Tala - All rights reserved

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