Language Specification of CIT’s First Programming Language (CFPL)

Usage

  # python interpreter.py tests/test1.txt

Introduction

CFPL is a very simple programming language that allows the programmer to achieve fluency in minutes. It is a strongly typed programming language. It is intended for students enrolled in programming languages. It aims to train them on how to build a pure interpreter.

Sample Program:

* my first program in CFPL
VAR abc, b, c AS INT
VAR x, w_23='w' AS CHAR
VAR t="TRUE" AS BOOL
START
  abc=b=10
  w_23=’a’
  * this is a comment
  OUTPUT: abc & “hi” & b & “#” & w_23 & “[#]”
STOP

Output of the sample program:

10hi10
a#

Language Grammar

Program Structure:

• every line contains a single statement
• all variable declaration is found on top of the program
• a line that starts with asterisk(*) is considered as a comment and comment can be found in any part of the program
• executable code should be found inside the START and STOP block - all reserved words are in capital letters
• sharp sign(#) signifies next line or carriage return
• ampersand(&) serves as a concatenator
• the square braces([]) are as escape code

Data Types:

INT – an ordinary number with no decimal part. It uses 32 bits. It can be positive or negative. (default: 0)
CHAR – a single symbol. It uses UNICODE. (default:"")
BOOL – represents the literals "TRUE" or "FALSE". (default: "FALSE")
FLOAT – a number with decimal part. It uses 64 bits. (default: 0)

Operators:

Arithmetic operators

( )         - parenthesis
*, /, %     - multiplication, division, modulo
+, -        - addition, subtraction
>, <        - greater than, lesser than
>=, <=      - greater than or equal to, lesser than or equal to
==, <>      - equal, not equal

Logical operators ()

AND         - needs the two BOOL expression to be true to result to true, else false
OR          - if one of the BOOL expressions evaluates to true, returns true, else false
NOT         - the reverse value of the BOOL value (NOT <BOOL expression>)

Unary operator

+           - positive
-           - negative

Sample Programs

1. A program with arithmetic operation

VAR xyz, abc=100 AS INT
START
  xyz= ((abc *5)/10 + 10) * -1
  * xyz should have the value -60
  OUTPUT: "[[]" & xyz & "[]]"
STOP

Output of the sample program:

[-60]

2. A program with logical operation

VAR a=100, b=200, c=300 AS INT
VAR d="FALSE" AS BOOL
START
  d = (a < b AND c <>200)
  OUTPUT: d
STOP

Output of the sample program:

TRUE

CFPL Control structures allows programmers to develop codes that will support commands with decision making capabilities.

1. Control structures a. If statement

- IF (<BOOL expression>)
    START
      <statement>
      ...
      <statement>
    STOP

b. If-else statement

- IF (<BOOL expression>)
    START
      <statement>
      ...
      <statement>
    STOP
- ELSE
    START
      <statement>
      ...
      <statement>
    STOP

c. While statement

- WHILE (<BOOL expression>)
    START
      <statement>
      ...
      <statement>
    STOP

2. INPUT – allow the user to input a value to a data type. Syntax:

INPUT: <variableName>[,<variableName>]*

Sample use:

INPUT: x, y

• means in the screen you have to input two values separated by comma(,)