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Déjà Vu

It is a programming language. Stack-based. Semi-functional. Backwards. Inspired by Python and Forth. I'm talking about Déjà Vu.

Setting up the virtual machine

$ cd vm/
$ make
$ cd ..

Running things

Assuming you have a module called yourfile.deja, you can compile and run it with:

$ vm/vu yourfile.deja

Examples

Hello world

!print "Hello world!"

Fibonacci

fib a:
    if > 1 a:
        fib - 1 a
        fib - 2 a
        +
    elseif = a 1:
        1
    else:
        0

Quine

"!print !. dup"
!print !. dup

Fractions

. * 1/3 3/2 # prints 1/2

Grammar

If you know what BNF is, here's the one for Déjà Vu:

Program ::= <Block>*

Block ::= <Head> ":" <NewLine>+ (<Indentation> <Block>)+
        | <Line> <NewLine>+
        | <IfBlock>
        | <TryBlock>

IfBlock ::= "if" <Space> <Line> ":" <NewLine>+ (<Indentation> <Block>)+
            ("elseif" <Space> <Line> <Space>? ":" <NewLine>+ (<Indentation> <Block>)+)*
            ("else" <Space>? ":" <NewLine>+ (<Indentation> <Block>)+)?

TryBlock ::= "try" <Space>? ":" <NewLine>+ (<Indentation> <Block>)+
             ("catch" (<Space> <ProperWord>)+ <Space>? ":" <NewLine>+ (<Indentation> <Block>)+)*

Head ::= "while" <Space> <Line>
       | "for" <Space> <ProperWord> (<Space> <Line>)? <Space>?
       | "repeat" <Space> <Line>
       | "func" <Space> <ProperWord> <Arguments>
       | "local" <Space> <ProperWord> <Arguments>
       | "labda" <Arguments>
       | <ProperWord> <Arguments>

Indentation ::= (" " | <Tab>)*

Line ::= (<Word> (<Space> <Word>)*)? <Space>?

Arguments ::= (<Space> <ProperWord>)* <Space>?

Space ::= (" " | <Tab>)+

Word ::= ProperWord
       | Get
       | Identity
       | String
       | Number
       | Fraction

Get ::= "@" <ProperWord>?

Identity ::= ":" <ProperWord>?

ProperWord ::= <Char>+

String ::= '"' <StringChar>* '"'

Number ::= '-'? <Digits> ('.' <Digits>)?

Fraction ::= '-'? <Digits> '/' <Digits>

Digits ::= ('0'..'9')+

Char ::= any non-whitespace, non-# character

StringChar ::= any character other than a double quote
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