examples required features

Cargo.toml

@@ -12,10 +12,14 @@ build = "build.rs"
 rustc_version = "0.2"
 
 [dependencies]
-rustc-hex = "1.0"
+rustc-hex = { version = "1.0", optional = true }
 heapsize = { version = "0.4", optional = true }
 byteorder = { version = "1", default-features = false }
 
 [features]
 heapsizeof = ["heapsize", "std"]
-std = []
+std = ["rustc-hex"]
+
+[[example]]
+name = "modular"
+required-features = ["std"]

src/uint.rs

@@ -1433,6 +1433,7 @@ impl From<U256> for u32 {
 known_heap_size!(0, U128, U256);
 
 #[cfg(test)]
+#[cfg(std)]
 mod tests {
 	use uint::{U128, U256, U512};
 	use std::str::FromStr;