19f7ad09a7
Add conditional expressions of the form:
foo := if lhs == rhs { then } else { otherwise }
`lhs`, `rhs`, `then`, and `otherwise` are all arbitrary expressions, and
can recursively include other conditionals. Conditionals short-circuit,
so the branch not taken isn't evaluated.
It is also possible to test for inequality with `==`.
48 lines
1.2 KiB
Rust
48 lines
1.2 KiB
Rust
use crate::common::*;
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pub(crate) struct Variables<'expression, 'src> {
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stack: Vec<&'expression Expression<'src>>,
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}
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impl<'expression, 'src> Variables<'expression, 'src> {
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pub(crate) fn new(root: &'expression Expression<'src>) -> Variables<'expression, 'src> {
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Variables { stack: vec![root] }
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}
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}
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impl<'expression, 'src> Iterator for Variables<'expression, 'src> {
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type Item = Token<'src>;
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fn next(&mut self) -> Option<Token<'src>> {
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match self.stack.pop() {
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None
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| Some(Expression::StringLiteral { .. })
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| Some(Expression::Backtick { .. })
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| Some(Expression::Call { .. }) => None,
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Some(Expression::Conditional {
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lhs,
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rhs,
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then,
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otherwise,
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..
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}) => {
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self.stack.push(lhs);
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self.stack.push(rhs);
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self.stack.push(then);
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self.stack.push(otherwise);
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self.next()
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},
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Some(Expression::Variable { name, .. }) => Some(name.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 { contents }) => {
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self.stack.push(contents);
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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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