vendor pretty-print dep

pretty-print/Readme.md

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+# Pretty Printer
+
+This crate defines a
+[Wadler-style](http://homepages.inf.ed.ac.uk/wadler/papers/prettier/prettier.pdf)
+pretty-printing API.
+
+Start with the static functions of [PrettyTree](enum.Doc.html).
+
+## Quick start
+
+Let's pretty-print simple sexps!  We want to pretty print sexps like
+
+```lisp
+(1 2 3)
+```
+or, if the line would be too long, like
+
+```lisp
+((1)
+ (2 3)
+ (4 5 6))
+```
+
+A _simple symbolic expression_ consists of a numeric _atom_ or a nested ordered _list_ of
+symbolic expression children.
+
+
+
+```rust
+use pretty_print::*;
+use SExp::*;
+enum SExp {
+    Atom(u32),
+    List(Vec<SExp>),
+}
+
+impl SExp {
+    /// Return a pretty printed format of self.
+    pub fn to_doc(&self) -> PrettyTree {
+        match self {
+            Atom(x) => PrettyTree::text(x.to_string()),
+            List(xs) => PrettyTree::text("(")
+                .append(PrettyTree::join(xs.into_iter().map(|x| x.to_doc()), PrettyTree::line_or_space()).nest(1).group())
+                .append(PrettyTree::text(")")),
+        }
+    }
+    /// Return a pretty printed format of self.
+    pub fn to_pretty(&self, width: usize) -> String {
+        let mut w = Vec::new();
+        self.to_doc().render(width, &mut w).unwrap();
+        String::from_utf8(w).unwrap()
+    }
+}
+
+fn main() {
+    let atom = Atom(5);
+    assert_eq!("5", atom.to_pretty(10));
+    let list = List(vec![Atom(1), Atom(2), Atom(3)]);
+    assert_eq!("(1 2 3)", list.to_pretty(10));
+    assert_eq!(
+        "\
+(1
+ 2
+ 3)",
+        list.to_pretty(5)
+    );
+}
+```