Gengo

Gengo. Pet programming language build for fun.

Features (release 1.0.0)

• Reading from console
• Reading from files
• Functions
• Arrays (with built-in functions: size, push, pop)
• Strings (with built-in functions: length)
• 64-bit Integers and Floats (int, float)
• General built-in functions: print
• Error messages

Examples

Concatenate array of strings:

array arr = ["1", "2", "3", "4", "5"];

function concat(a: array) -> string {
	int sz = size(a);
	string res = "";

	loop(int i = 0; i < sz; i = i + 1) {
		res = res + a[i];
	};

	return res;
};

print(arr);
print(concat(arr));

[1, 2, 3, 4, 5]
12345

'Hello World!' program:

string str = "Hello World!";
print(str);
print(length(str));

Hello World!
12

Factorial of a number:

function factorial(a: int) -> int {
	if(a == 0) {
		return 1;	
	}
	otherwise {
		return a * factorial(a - 1); 
	};
};

print(factorial(10));

3628800

Language Grammar

Language Entity	Ruleset
statements	expr NEWLINE (expr NEWLINE)*
statement	expr
	KEYWORD:return expr
expr	(KEYWORD:TYPE)? IDENTIFIER EQ expr
	comp-expr
comp-expr	arith-expr ((AND|OR|EQEQ|NE|GT|GTE|LT|LTE) arith-expr)*
arith-expr	term ((PLUS|MINUS) term)*
term	factor ((MUL|DIV) factor)*
factor	INT|FLOAT|STRING|IDENTIFIER
	IDENTIFIER LPAREN (expr (COMMA expr)*)? RPAREN
	IDENTIFIER LSQUARE expr RSQUARE (LSQUARE expr RSQUARE)* (EQ expr)?
	(PLUS|MINUS) factor
	LPAREN comp-expr RPAREN
	NOT comp-expr
	array-expr
	if-expr
	for-expr
	func-def
func-def	KEYWORD:function IDENTIFIER LPAREN (IDENTIFIER COLON KEYWORD:TYPE
	(COMMA IDENTIFIER COLON KEYWORD:TYPE)*)? RPAREN ARROW KEYWORD:TYPE
	LBRACE statements RBRACE
if-expr	KEYWORD:if LPAREN expr RPAREN LBRACE statements RBRACE
	(if-else-expr|else-expr)?
if-else-expr	KEYWORD:elif LPAREN expr RPAREN LBRACE statements RBRACE
	(if-else-expr|else-expr)?
else-expr	KEYWORD:otherwise LBRACE statements RBRACE
for-expr	KEYWORD:loop LPAREN (expr)? NEWLINE expr NEWLINE (expr)? RPAREN LBRACE statements RBRACE
array-expr	LSQUARE (expr (COMMA expr)*)? RSQUARE

Features (pre-release 0.6.0)

• Strings
• Built-in Functions (print, size)

Snippets (strings, built-in functions)

Strings:

gengo > string s = "Hello World!";
Hello World!

New built-in functions:

string s1 = "What does ";
string s2 = "'Gengo' ";
string s3 = "mean?";

gengo > print(s1 + s2 + s3);
What does 'Gengo' mean?

string name = "Dmitrii Art"

gengo > print(size(name));
11

0.5.0 (alpha) Pre-release functionality

Features (pre-release 0.5.0)

• Functions
• Recursion support

Snippets (functions)

Function declaration:

function add(a: int, b: int) -> int {
	return a + b;
};

function sum(a: int) -> int {
	if (a == 0) {
		return 0;
	}
	otherwise {
		return a + sum(a - 1);
	};
};

Function call:

gengo > add(10, 15 - 1);
24

gengo > sum(3);
6

Features (pre-release 0.4.0)

• For loops (with correct scope management)

Snippets (loops)

For-loop:

gengo > int a = 1;
1
gengo > loop(int i = 0; i < 10; i = i + 1){ a = a * 2; };
gengo > a;
gengo > 1024

Features (pre-release 0.3.0)

• Comparison expressions
• Conditions (with correct scope management)

Snippets (comparisons, conditions)

Simple comparisons:

gengo > 1 > 0;
1
gengo > 100 != 99 + 1 - 1;
1

Variables included

gengo > int a = 10; int b = 11;
11 - returns `b` (last statement) as a result of operation
gengo > a <= b;
1

Conditions (returns last statement result):

gengo > int a = 10;
10
gengo > if (a == 10) { a = 11; } elif (a == 11) { a = 12; } otherwise { a = 10; };
11
gengo > if (a == 10) { a = 11; } elif (a == 11) { a = 12; } otherwise { a = 10; };
12
gengo > if (a == 10) { a = 11; } elif (a == 11) { a = 12; } otherwise { a = 10; };
10
gengo > a;
10

Features (pre-release 0.2.0)

• Initializing and using variables
• Error messages

Snippets (variables)

Initialization and assigning (supported types - int, float):

gengo > int a = 10
10
gengo > a = a - 11
-1

gengo > float b = 10
10.000000
gengo > b / 3
3.333333

Initialization and assigning 'queue':

gengo > int t = int c = 10
10
gengo > t
10
gengo > c
10

gengo > int d = float b = 10
10 - returns `d` as a result of operation
gengo > d
10
gengo > b
10.000000

Errors printing:

gengo > int a = 10
10
gengo > a = a + b
Calls trace:
File <console input>
Run Time Error:'b' is not defined

Features (pre-release 0.1.0)

• Supports arithmetic operations in console
• Correct order of binary and unary operations
• Print the structure of AST (Token representation)
• Auto int/float casting

Snippets (arithmetic operations)

Basic operations (+, -, *, /):

gengo > 1 + 2 * 4
(INT:1, PLUS, (INT:2, MULT, INT:4))
9

Unary operations:

gengo > ---1 + 100
((MINUS, (MINUS, (MINUS, INT:1))), PLUS, INT:100)
99

Correct order of operations:

gengo > (1 + 2) * 4
12
gengo > 1 + 2 * 4
9
gengo > 10 / 2 + 4
9

Types casting:

gengo > 2 * 4.5 - 1
((INT:2, MULT, FLOAT:4.5), MINUS, INT:1)
8.000000