68 lines
No EOL
1.5 KiB
Markdown
68 lines
No EOL
1.5 KiB
Markdown
# Pretty Printer
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This crate defines a
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[Wadler-style](http://homepages.inf.ed.ac.uk/wadler/papers/prettier/prettier.pdf)
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pretty-printing API.
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Start with the static functions of [PrettyTree](enum.Doc.html).
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## Quick start
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Let's pretty-print simple sexps! We want to pretty print sexps like
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```lisp
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(1 2 3)
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```
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or, if the line would be too long, like
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```lisp
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((1)
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(2 3)
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(4 5 6))
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```
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A _simple symbolic expression_ consists of a numeric _atom_ or a nested ordered _list_ of
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symbolic expression children.
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```rust
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use pretty_print::*;
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use SExp::*;
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enum SExp {
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Atom(u32),
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List(Vec<SExp>),
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}
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impl SExp {
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/// Return a pretty printed format of self.
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pub fn to_doc(&self) -> PrettyTree {
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match self {
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Atom(x) => PrettyTree::text(x.to_string()),
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List(xs) => PrettyTree::text("(")
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.append(PrettyTree::join(xs.into_iter().map(|x| x.to_doc()), PrettyTree::line_or_space()).nest(1).group())
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.append(PrettyTree::text(")")),
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}
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}
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/// Return a pretty printed format of self.
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pub fn to_pretty(&self, width: usize) -> String {
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let mut w = Vec::new();
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self.to_doc().render(width, &mut w).unwrap();
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String::from_utf8(w).unwrap()
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}
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}
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fn main() {
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let atom = Atom(5);
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assert_eq!("5", atom.to_pretty(10));
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let list = List(vec![Atom(1), Atom(2), Atom(3)]);
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assert_eq!("(1 2 3)", list.to_pretty(10));
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assert_eq!(
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"\
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(1
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2
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3)",
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list.to_pretty(5)
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);
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}
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``` |