jnr Programming Language

A simple interpreted programming language built with Flex and Bison for CSC 112.

Project Structure

jnr/
├── src/                    # Source files
│   ├── jnr.l              # Flex lexer
│   └── jnr.y              # Bison parser
├── tests/                  # Test programs
│   ├── test.jnr           # Basic test
│   ├── test_types.jnr     # All types demo
│   ├── test_int.jnr       # Integer operations
│   ├── test_char.jnr      # Character handling
│   ├── test_comma_declarations.jnr  # Comma-separated declarations
│   ├── test_input.jnr     # Interactive input test
│   └── simple.jnr         # Minimal test
├── docs/                   # Documentation
│   ├── README.md          # You're Here
├── scripts/                # Helper scripts
│   └── run_test.sh        # Test runner
├── Makefile               # Build automation
└── jnr                    # Compiled executable

Features

• Typed variable declarations (int, char)
• Comma-separated declarations (e.g., int x = 10, y, z = 30!)
• Arithmetic operations (+, -, *, /, %) with proper precedence
• Comparison operations (<, >, <=, >=, ==, !=)
• Print function (show()) with type-aware output
• Input function (ask()) for integers
• Parenthesized expressions
• Hash-style comments (#)

Grammar (BNF)

PROGRAM        → 'start' '(' ')' '{' STATEMENT_LIST '}'
STATEMENT_LIST → STATEMENT | STATEMENT_LIST STATEMENT
STATEMENT      → DECLARATION '!' | ASSIGNMENT '!' | PRINT_FUNC '!' | INPUT_FUNC '!'
DECLARATION    → 'int' VAR_LIST_INT
               | 'char' VAR_LIST_CHAR
VAR_LIST_INT   → identifier
               | identifier '=' EXPRESSION
               | VAR_LIST_INT ',' identifier
               | VAR_LIST_INT ',' identifier '=' EXPRESSION
VAR_LIST_CHAR  → identifier
               | identifier '=' CHARLIT
               | VAR_LIST_CHAR ',' identifier
               | VAR_LIST_CHAR ',' identifier '=' CHARLIT
ASSIGNMENT     → identifier '=' EXPRESSION
PRINT_FUNC     → 'show' '(' EXPRESSION ')'
               | 'show' '(' identifier ')'
               | 'show' '(' CHARLIT ')'
INPUT_FUNC     → 'ask' '(' identifier ')'
EXPRESSION     → EXPRESSION '+' EXPRESSION
               | EXPRESSION '-' EXPRESSION
               | EXPRESSION '*' EXPRESSION
               | EXPRESSION '/' EXPRESSION
               | EXPRESSION '%' EXPRESSION
               | EXPRESSION '<' EXPRESSION
               | EXPRESSION '>' EXPRESSION
               | EXPRESSION '<=' EXPRESSION
               | EXPRESSION '>=' EXPRESSION
               | EXPRESSION '==' EXPRESSION
               | EXPRESSION '!=' EXPRESSION
               | '(' EXPRESSION ')'
               | number
               | identifier
CHARLIT        → 'any_char'

Building

# Generate parser and lexer
make

# Or manually:
bison -d src/jnr.y      # Generates jnr.tab.c and jnr.tab.h
flex src/jnr.l          # Generates lex.yy.c
gcc jnr.tab.c lex.yy.c -o jnr

Usage

Running from file (without input())

./jnr < tests/test.jnr

Running specific tests

make test              # Run basic test
make test-types        # Test all types
make test-int          # Test integers
make test-char         # Test characters
make test-all          # Run all tests

Running programs with ask() function

For programs using ask(), you have two options:

Option 1: Interactive Mode (Recommended)

./jnr
# Paste or type your code
# Press Ctrl+D when done
# Type input values when prompted

Option 2: Using a shell script

./scripts/run_test.sh

Interactive mode (best for testing)

./jnr
# Type your code, then press Ctrl+D to run

Example Program

Type Declarations with Comma-Separated Variables

start() {
    # Multiple variables in one statement
    int x = 10, y = 5, sum!
    sum = x + y!
    show(sum)!

    # Character type
    char c = 'A'!
    show(c)!

    # Mixed initialization
    int a = 100, b, c = 200!
    show(a)!  # 100
    show(b)!  # 0 (default)
    show(c)!  # 200
}

Output:

Welcome to jnr! (Type your code, Press Ctrl+D to run)
15
A
100
0
200

Sample Output (Without Input)

For the basic test (tests/test.jnr without input):

Welcome to jnr! (Type your code, Press Ctrl+D to run)
15
50

Notes

• All programs must be wrapped in start() { ... } - This is required structure
• Programs using ask() are best run in interactive mode
• The ask() function reads integers from stdin
• Use file mode (./jnr < file.jnr) for programs without input
• Arithmetic follows standard precedence: *, /, % before +, -
• Comparison operators return 1 (true) or 0 (false)
• Variables can be any identifier starting with a letter
• Statements must end with ! exclamation mark
• Comments start with # and continue to end of line
• JNR v5.0 requires start() {} structure and supports only int and char types

Documentation

See docs/CHANGELOG.md for complete development history and all implementation details.