rathrio/pl0

Interpreter for a small toy language.

PL0 - Tiny programming language interpreter

Interpreter for a small toy language.

Usage

pl0 path/to/program

Sample Programs

Hello World

p "Hello World"

Arithmetics

p 2 + 2
foo = 4
bar = 24
baz = (foo + bar) / 3
p baz

Conditionals

bar = 2

while (bar < 99) {
    bar = bar + 2

    if (bar == 8) {
        p "blabla"
    } else {
        p "dog"
    }

    p bar
}

Grammar

program           := statements?
statements        := statement (t statement)*
t                 := '\n'
statement         := if_else_statement | while_statement | assignment | print_statement | exp
if_else_statement := 'if' '(' exp ')' '{' statements? '}' 'else' '{' statement* '}'
while_statement   := 'while' '(' exp ')' '{' statements? '}'
assignment        := identifier '=' exp
print_statement   := 'p' exp
exp               := add_exp ( ( '<' | '>' | '<=' | '>=' | '==' ) add_exp )?
add_exp           := mult_exp ( ( '+' | '-' ) mult_exp )*
mult_exp          := prefix_exp ( ( '*' | '/' | '%' ) prefix_exp )*
prefix_exp        := not_exp | prim_exp
not_exp           := ('!')* exp
prim_exp          := identifier | paren_exp | int_lit | true_lit | false_lit | string_lit | function | function_call
paren_exp         := '(' exp ')'
int_lit           := [0-9] [0-9]*
true_lit          := 'true'
false_lit         := 'false'
string_lit        := '"' (!('"'))* '"'
function          := 'f' '(' arg_list? ')' '{' statements? '}'
arg_list          := id (',' id)*

Running tests

ruby pl0_test.rb