PLATYPUS Compiler

A compiler for the PLATYPUS programming language that transpiles to C. Originally developed as a compilers course project (CST8152), extended with a full C code generator.

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        PLATYPUS → C Transpiler

Quick Start

# Build the compiler
./build.sh

# Compile a PLATYPUS program to executable
./platyc program.pls

# Run it
./program

Repository Structure

platypus/
├── compiler/           # Source code
│   ├── buffer.c/h      # Input buffer management
│   ├── scanner.c       # Lexical analyzer (tokenizer)
│   ├── table.h         # Scanner transition tables & token definitions
│   ├── token.h         # Token type definitions
│   ├── parser.c/h      # Syntax analyzer (validates grammar)
│   ├── codegen.c/h     # C code generator module
│   ├── transpiler.c    # Main transpiler (parser + code emission)
│   ├── platy.c         # Parser-only driver (syntax checking)
│
├── spec/               # Language specification
│   ├── language-spec.md    # Full grammar and semantics
│   ├── syntax-spec.md      # Syntax details
│   └── transition-diagram.png  # Scanner state machine
│
├── test-files/         # Test programs
│   ├── source/         # .pls source files
│   └── result/         # Expected outputs
│
├── build/              # Compiled binaries (gitignored)
├── build.sh            # Build script
├── Makefile            # Alternative build system
└── platyc              # Compiler driver script

Build Tools

Command	Description
./build.sh	Build all tools
make	Same as build.sh
make clean	Remove build artifacts

Generated Executables

Binary	Purpose
build/platy_trans	Transpiler: PLATYPUS → C source
build/platypus	Syntax checker only
build/platy_scanner	Tokenizer only

Usage

Compile and Run (Recommended)

# One-step compile to executable
./platyc myprogram.pls

# With custom output name
./platyc myprogram.pls myapp

# Run
./myprogram   # or ./myapp

Manual Steps

# Step 1: Transpile to C
./build/platy_trans myprogram.pls

# Step 2: Compile C to executable  
gcc -o myprogram myprogram.c

# Step 3: Run
./myprogram

Syntax Check Only

./build/platypus myprogram.pls

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PLATYPUS Language Reference

Program Structure

Every PLATYPUS program is wrapped in PLATYPUS { }:

PLATYPUS {
    !! Your code here
}

Comments

Single-line comments start with !!:

!! This is a comment
a = 10;  !! Inline comment

Variables

Variables are implicitly declared on first use. Type is inferred from name:

Suffix	Type	Example
(none)	Numeric (float)	count, total
$	String	name$, msg$

count = 42;           !! Numeric variable
pi = 3.14159;         !! Also numeric
greeting$ = "Hello";  !! String variable

Naming rules:

• First character must be a letter (a-z, A-Z)
• Followed by letters or digits
• Maximum 8 significant characters
• String variables end with $

Data Types

Type	Literals	Examples
Integer	Decimal digits	0, 42, 999
Float	Decimal with .	3.14, 0.5, 100.
String	Double-quoted	"Hello", "World"

Operators

Arithmetic

Operator	Meaning
+	Addition / Unary plus
-	Subtraction / Unary minus
*	Multiplication
/	Division

String

Operator	Meaning
#	Concatenation

full$ = first$ # " " # last$;

Relational

Operator	Meaning
==	Equal
<>	Not equal
<	Less than
>	Greater than

Logical

Operator	Meaning
.AND.	Logical AND
.OR.	Logical OR

Statements

Assignment

variable = expression;
string$ = string_expression;

Input (READ)

READ(variable);
READ(a, b, c);  !! Multiple variables

Output (WRITE)

WRITE("Hello World!");     !! String literal
WRITE(variable);           !! Single variable
WRITE(a, b, c);            !! Multiple variables
WRITE();                   !! Empty line

Selection (IF)

PLATYPUS has a unique IF syntax with a pre-condition (TRUE or FALSE):

IF TRUE(condition) THEN {
    !! Executes when condition is TRUE
} ELSE {
    !! Executes when condition is FALSE
};

IF FALSE(x == 0) THEN {
    !! Executes when x == 0 is FALSE (i.e., x != 0)
} ELSE {
    !! Executes when x == 0 is TRUE (i.e., x == 0)
};

Note: Both THEN and ELSE blocks are required (can be empty).

Iteration (WHILE)

Similar pre-condition syntax:

WHILE TRUE(condition) REPEAT {
    !! Loop while condition is TRUE
};

WHILE FALSE(x > 10) REPEAT {
    !! Loop while x > 10 is FALSE (i.e., x <= 10)
};

Complete Example

!! Factorial calculator
PLATYPUS {
    WRITE("Enter a number:");
    READ(n);
    
    result = 1;
    counter = 1;
    
    WHILE TRUE(counter < n .OR. counter == n) REPEAT {
        result = result * counter;
        counter = counter + 1;
    };
    
    WRITE("Factorial is:");
    WRITE(result);
}

Grammar Summary

<program>       → PLATYPUS { <opt_statements> }
<statements>    → <statement> | <statements> <statement>
<statement>     → <assignment> | <selection> | <iteration> 
                | <input> | <output>

<assignment>    → AVID = <arith_expr> ; | SVID = <str_expr> ;
<selection>     → IF <pre> ( <cond_expr> ) THEN { <opt_stmts> } 
                  ELSE { <opt_stmts> } ;
<iteration>     → WHILE <pre> ( <cond_expr> ) REPEAT { <stmts> } ;
<input>         → READ ( <var_list> ) ;
<output>        → WRITE ( <output_list> ) ;

<pre>           → TRUE | FALSE
<arith_expr>    → <term> | <arith_expr> +/- <term>
<str_expr>      → <str_primary> | <str_expr> # <str_primary>
<cond_expr>     → <log_or_expr>

Error Messages

The transpiler provides detailed error messages with line numbers:

Error at line 5: expected ';', found arithmetic variable 'x'
Error at line 12: expected keyword 'THEN', found '}'

Limitations

• No functions or procedures
• No arrays
• No nested scopes (all variables global)
• String literals cannot contain " or newlines
• Maximum 8 significant characters in identifiers

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License

Educational project. Original course materials by Svillen Ranev (Algonquin College). Transpiler extension by Marco Gregory.