BICPP-Basic_Interpreter_in_CPP

Description

It's basic interpreter written in C++.

Introduction

To compile project advised is gcc compiler. It doesn't required any libraries to compile. You can compile project by downloading it, opening folder. Next you should open terminal and print the command (linux or windows)

g++ main.cpp -o main.exe

To run compiled program in windows you can do it by double click main.exe in linux you must print the command (if you are in the folder with project).

.\main.exe

After runing compiler you should see information bellow.

Basic interpreter example implementation
Version: A0.03
>>>

You can print commands! If you want interrupt program working you can do it by typing ESC key.

Syntax

In basic language commands should by written with capital letters, but in the version you don't have to do it, because interpreter do it. Interpreter works in immedidate and execution mode. In immediate mode program is executed without delay. If you want work in the mode you must write command without number line for example

PRINT "HI"

In execution before command must be line number.

10 PRINT "HI"

Variables

Integer variable in the basic interpreter is marked by % on the end of name. For example:

INTVAR%

If you want to write integer in hexadecimal code you must write at the end of constant letter H. For example: A1H is 161 in decimal code.
Float variables and constants are known in Basic language as numeric, which aren't marked by any char at the end. For exapmple:

NUMVAR

Integer and numeric variable or constants have the same operator, which are:

• + add two numbers (e.g.: 2+2 returns 4);
• - substract two numbers (e.g.: 4-2 returns 2);
• / divide two numbers (e.g.: 8/2 returns 4);
• * multiply two numbers (e.g.: 8*2 returns 16);
• ^ raise a number to power (e.g.: 8^2 returns 64);

Attention! If expression consist of integer result will be integer so you lose information after the decimal separator e.g.: 7/2 result is 3 not 3.5. If you want, that result will be numeric you must write it as numeric e.g.: 7.0/2.0 returns 3.5.
You can place expression in round brackets, which influencs sequences of operations e.g.: 2+2/2 returns 3 but (2+2)/2 returns 2.

String is text, which must be enclosed in a pair of " and it's doesn't changed by interpreter to capital letter and more than one space aren't deleted. If you want create string variable, name of it must marked by $ on the end. For example:

STRVAR$

If you want add " in the text you must write " before ". For example:

" If you want print ""Hello World"" on terminal you must use the command: ""PRINT ""Hello World"""

String operator are:

• & which concatenate text; If you write it in command line:

  "abcd"&"abcd"

  you get:

  abcdabcd

• [n:m] which returns substring from text for n to m char, where first char has number 0 e.g.: "abcd"[1:2] returns bc

Arrays aren't available yet.

Array can be int, string and numeric and at end of name, but before bracker, you must give the same marked. For example:

STRARRAY$(4)

It's array, which store five strings. If you want create 2 dimensional array you can do it at the way:

STRARRAY$(4,2)

The array consist of 5 rows and 3 columns.

Integer, numeric and string value can be compared by relational operator, which are:

• > returns true, when left value is bigger than right;
• >= returns true, when left value is bigger or equal to right;
• < returns true, when right value is bigger than left;
• <= or =< returns true, when right value is bigger or equal left;
• = or == returns true, when left value is equal to right;
• <> or != returns true, when left value is unequal to right;

You must remember, that numeric value are converted to int value before compare.

Result of relation operations or numbers can be checked by logical operators, which are:

• NOT deny term (e.g.: NOT 1 return 0);
• AND return 1 only if left and right term is 1 (e.g.: 1 AND 0 return 0 but 1 AND 1 return 1);
• OR return 1 if even one term is 1 (e.g.: 1 OR 1 return 1 and 1 OR 0 return 1);
• XOR return 1 if one term is 1 (e.g.: 1 XOR 1 return 0 but 1 XOR 0 return 1);
• IMP return 1 if two terms are 1 or 1 or first terms is 1 and second term is 1 (e.g.: 0 IMP 0 return 1 and 0 IMP 1 return 1 but 1 IMP 0 return 0);
• EQV return 1 only if two term are 0 or 1 (e.g.: 1 EQV 1 return 1 but 1 EQV 0 return 0).

Statements

Statements allows to edit text, clear memory, take input and other thing. Bellow you can read description about each statements.

RUN

The statement start to interpret program stored in program memory. It does't take any arguments.

CLEAR

The statement clear program and variable memory. It doesn't take any argument.

LET

The statement allow to assign value to variable for example:

LET x% = 1

assign 1 to variable x%. At the right of the equal sign can be equation, variable constants, logical an relation operation.

INPUT

It allows you to input text or numbers to program and assign it to variable e.g.:

INPUT "->" A$

displays ->, which is prompt ask you for print something. After press enter your input will be assign to A$ variable.

PRINT

Print statement allows to print on output e.g.:

PRINT "Variable value: ", A$

displays literal writing after print and value of A$ variable. Argument of the statement must by separated by comma.

REM

This statement allow you to add comment in your code. If you write it at the begining of the line it won't be interpreted and executed.

GOTO

GOTO statement allows to go to any line of program storaged in memory. Argument must be integer constant e.g.:

GOTO 10

it jumps program to ten lines.

IF

If statement allows to do command if term is equal or bigger than 0. Term can be number, logical, relation operation and string.

IF X>10 THEN PRINT "X is bigger than 10"

Command written behind THEN will be executed if x is bigger than 10.