35 lines
832 B
Rust
35 lines
832 B
Rust
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use crate::common::*;
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pub struct Variables<'a> {
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stack: Vec<&'a Expression<'a>>,
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}
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impl<'a> Variables<'a> {
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pub fn new(root: &'a Expression<'a>) -> Variables<'a> {
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Variables { stack: vec![root] }
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}
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}
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impl<'a> Iterator for Variables<'a> {
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type Item = &'a Token<'a>;
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fn next(&mut self) -> Option<&'a Token<'a>> {
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match self.stack.pop() {
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None
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| Some(Expression::String { .. })
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| Some(Expression::Backtick { .. })
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| Some(Expression::Call { .. }) => None,
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Some(Expression::Variable { token, .. }) => Some(token),
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Some(Expression::Concatination { lhs, rhs }) => {
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self.stack.push(lhs);
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self.stack.push(rhs);
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self.next()
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}
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Some(Expression::Group { expression }) => {
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self.stack.push(expression);
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self.next()
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}
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}
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}
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}
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