Eryn Wells
d825d0ec8a
Reconfigure the top-level object types. - Obj is an enum pointer type - Object is a trait that all Scheme types should implement Define Sym, a symbol type. Define Pair, a pair/cons/list type. Implement Display for all types above. Implement casting methods for the above.
41 lines
1 KiB
Rust
41 lines
1 KiB
Rust
/* types/src/pair.rs
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* Eryn Wells <eryn@erynwells.me>
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*/
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use std::any::Any;
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use std::fmt;
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use super::*;
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use object::Object;
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pub struct Pair {
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car: Obj,
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cdr: Obj
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}
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impl Pair {
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fn fmt_pair(&self, f: &mut fmt::Formatter) -> fmt::Result {
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let r = write!(f, "{}", self.car);
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r.and_then(|r| match self.cdr {
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Obj::Null => Ok(r), // Don't write anything.
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Obj::Ptr(ref next) => {
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match next.as_pair() {
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Some(next_pair) => write!(f, " ").and_then(|_| next_pair.fmt_pair(f)),
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None => write!(f, " . {}", next)
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}
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}
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})
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}
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}
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impl Object for Pair {
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fn as_any(&self) -> &Any { self }
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fn as_pair(&self) -> Option<&Pair> { Some(self) }
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fn as_sym(&self) -> Option<&Sym> { None }
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}
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impl fmt::Display for Pair {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(f, "(").and_then(|_| self.fmt_pair(f))
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.and_then(|_| write!(f, ")"))
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}
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}
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