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use internal::parser;
use strconv;
use strings;
export type variable = (str, str);
export type interpreter = struct {
vars: []variable,
};
export type error = !(interperror | nomem);
export type interperror = !str;
export fn interpret(it: *interpreter, tree: parser::ast) void = {
match (tree.value) {
case parser::assign =>
assign(it, tree.children)!;
};
};
fn assign(it: *interpreter, nodes: []parser::ast) (void | error) = {
const varname = nodes[0].value as parser::varname;
const operation = nodes[1].value as parser::operation;
let value = 0;
let stack: []int = [];
for (let i = 0z; i < len(operation.stack); i += 1) {
const arg = operation.stack[i];
match (arg) {
case let i: int =>
append(stack, i)?;
case let o: parser::operator =>
if (len(stack) >= 2) {
let last = len(stack) - 1;
let val = switch (o) {
case parser::operator::ADD =>
yield stack[last] + stack[last-1];
case parser::operator::SUBTRACT =>
yield stack[last] - stack[last-1];
case parser::operator::MULTIPLY =>
yield stack[last] * stack[last-1];
case parser::operator::DIVIDE =>
yield stack[last] / stack[last-1];
};
delete(stack[last-1..]);
append(stack, val)?;
} else {
return "Invalid operation": interperror;
};
};
};
let last = len(stack) - 1;
append(it.vars, (varname, strings::dup(strconv::itos(stack[last]))?))?;
};
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