Description of VEPRAN language

1. Expressions

2. Variables

3. Functions and procedures

4. Types and declarations

5. Program structure

6. Operators

7. Error messages

8. Syntax

1. Expressions

1.1 Index - integer positive value , which takes values in the range 0 .. 65535

index operations :

comparison operations < > <= >= =

binary logical operations and, or

binary arithmetic operations + - div *

the unary logical not

unary arithmetic operators are + lg2 ex2

All the above operations are performed on the indexes and act in the body according to the descending order of precedence : unary ,binary arithmetic ,binary logical operations ,

comparison . In comparison operations and logical operations, TRUTH is induced by 0.

Example: a*b<c (a*b)<c 0 if a*b<c

not a div 2 (not a)/2 0/2 if а<>0

1.2 Expressions with slices

Expression of type SLICE can be

the mask M or

a variable of type SLICE.

Example: X

s (previously described slice s)

2. Variables

Variables can be of the following types:

INDEX

SLICE ,

user-defined type.

You can declare an array of variables of those types.

Constants was not typed and take integer values from 0 .. 65535 .

Example:

slice g[10],h,i[13];

const cOr=15;

3. Functions and procedures

You can write a procedure or function within another . Any function or procedure available only to the variables , parameters, and variables are described outside of the procedures and functions (global variables).

Possible recursive procedure calls. Specifiers settings REFER , CONST . CONST

preceded by immutable parameters REFER to parameters passed by reference . Specified before the type specifier applies to all list settings , then to the next parameter .

Specifier allows you to REFER passed as actual parameters to arrays of the specified type without control size .value returned value of the function should be assigned to the local variable RESULT.

Example:

FUNCTION func(REFER to index a[ ],CONST b; // variables passed by reference

// in this case b immutable

// a array without size

usertype c // a variable is passed by value

):slice; {function returns a value of type slice}

index d; {local variable}

begin

result:=x // returns the value of the register X

end;

4. Types and declarations

Description dynamic arrays allows you to specify and change the size of the array during program execution . For this purpose it is necessary to describe a variable as the array size , and then before the first

using execute the operator placement .

Example: program A;

index i[ ];

begin

index i[1+2];

i[0]:=1

end.

The program can present the description of the user type.

TYPE type_name=type;

where type is one of the designs

1 SLICE , INDEX , type_name

2 RECORD

type field_name1 , .. , field_nameK;

type field_nameN , .. , field_nameM

END

3 ARRAY [ size ] OF type

Further referencing variables user-defined type is a natural way : the fields through the point to elements of the array by specifying the index in square brackets . The elements of the array indexed by numbers from 0 to size-1.

Description of variables of this type : type_name name1,name2,..,nameK;

To describe the input data and results of the tasks are used accordingly keywords

The INPUT and OUTPUT .

Then describe variables of this type will be

INPUT INDEX var1,var2 ;// var1,var2 - input

OUTPUT INDEX var4,var5 ; // var4,var5 - output

INPUT OUTPUT INDEX var7,var8 ;//var7,var8 – input output

INPUT INDEX var10,OUTPUT var11;//var10 - input

// var11 - input output

When creating modules to include variables , functions or procedures in the interface part of the PUBLIC keyword is used.

Example:

PUBLIC procedure commonproc1; begin .. end ;

PUBLIC slice s;

P.S.: All external user-defined types are automatically included in the front-end part.

5. Program structure

PROGRAM program_name ;

external_modules

declaration_constants,types,variables,procedures,functions

body

6. Keywords

FOR .. [TO|DOWNTO] .. DO - loop type for

WHILE .. DO - loop type while

BREAK .. - operator interrupt cycle

CONTINUE .. - operator continue cycle

IF .. THEN .. [ ELSE .. ] - operator conditions

BEGIN - the beginning of the operator unit

End - the end of the operator unit

PROCEDURE - the beginning of a procedure Declaration

FUNCTION - beginning of the function Declaration

CONST - the beginning of the announcement of the list of constants specifier passing immutable parameter

INDEX - base type

SLICE - base type

DOWNTO - specifies the reverse direction account in the cycle type for

PROGRAM - program start

UNIT - start module

REFER - specifier passing a parameter by reference

TYPE - start ads user-defined type

RECORD .. END - announcement record fields

ARRAY [ .. ] OF - array declaration

PUBLIC - is an access specifier

USES - the beginning of the list of modules used

INPUT - the input specifier

OUTPUT - specifier input

X , Y , M - slice CPU registers

7. Error messages

The compiler scans the program until the first found error .

8. Syntax .

program::

PROGRAM program_name ;

external_modules

declaration_constants,types,variables,procedures,functions

body

module::

UNIT module_name ;

external_modules

declaration_constants,types,variables,procedures,functions

body

body::

begin operators_list end

operators_list::

operator

operator ; operators_list

operator::

blank

body

operator_index_assignment

operator_assignment

label : cycle_operator

cycle_operator

BREAK label

CONTINUE label

IF expression THEN operator

IF expression THEN operator ELSE operator

processor_command

allocation_operator

allocation_operator ::

type_name variable_name [ expression ]

cycle_operator::

FOR operator_index_assignment direction_attribute expression DO operator

FOR переменная TO expression direction_attribute operator

WHILE expression DO operator

direction_attribute::

DOWNTO

operator_index_assignment::

variable := expression

operator_assignment::

variable := variable

variable::

variable_name qualified_name

qualified_name::

blank

. field_name qualified_name

[ expression ] qualified_name

external_modules::

blank

USES modules_list ;

modules_list::

module_name

module_name , modules_list

declaration_constants,types,variables,procedures,functions::

LSP blank

LSP declaration_constants //