Use dtoa for better floating-point formatting

implementations/rust/preserves/Cargo.toml

@@ -13,6 +13,7 @@ gitlab = { repository = "preserves/preserves" }
 
 [dependencies]
 base64 = "0.13"
+dtoa = "0.4"
 num = "0.2"
 regex = "1.5"
 serde = { version = "1.0", features = ["derive"] }

implementations/rust/preserves/src/value/text/writer.rs

@@ -131,11 +131,13 @@ impl<W: io::Write> Writer for TextWriter<W> {
     }
 
     fn write_f32(&mut self, v: f32) -> io::Result<()> {
-        write!(self.0, "{:e}f", v)
+        dtoa::write(&mut *self.0, v)?;
+        write!(self.0, "f")
     }
 
     fn write_f64(&mut self, v: f64) -> io::Result<()> {
-        write!(self.0, "{:e}", v)
+        dtoa::write(&mut *self.0, v)?;
+        Ok(())
     }
 
     simple_writer_method!(write_i8, i8);