Create no_std examples

jaarg-nostd/examples/btreemap_nostd.rs

@@ -0,0 +1,46 @@
+/* btreemap_nostd - jaarg example program using BTreeMap in `no_std`
+ * SPDX-FileCopyrightText: (C) 2025 Gay Pizza Specifications
+ * SPDX-License-Identifier: MIT
+ */
+
+#![no_std]
+#![no_main]
+
+extern crate alloc;
+
+use jaarg::{
+  alloc::ParseMapResult, ErrorUsageWriter, ErrorUsageWriterContext, HelpWriter, HelpWriterContext,
+  Opt, Opts, StandardErrorUsageWriter, StandardFullHelpWriter
+};
+use jaarg_nostd::{eprint, print, println, harness::ExitCode, simplepathbuf::SimplePathBuf};
+
+#[no_mangle]
+#[allow(improper_ctypes_definitions)]
+extern "C" fn safe_main(args: &[&str]) -> ExitCode {
+  const OPTIONS: Opts<&'static str> = Opts::new(&[
+    Opt::help_flag("help", &["--help"]).help_text("Show this help"),
+    Opt::positional("positional", "positional").help_text("Positional argument"),
+    Opt::value("value", &["-v", "--value"], "string").help_text("Value option"),
+    Opt::flag("flag", &["-f", "--flag"]).help_text("Flag option"),
+  ]);
+
+  let map = match OPTIONS.parse_map(
+    SimplePathBuf::from(*args.first().unwrap()).basename(),
+    args.iter().skip(1),
+    |name| {
+      let ctx = HelpWriterContext { options: &OPTIONS, program_name: name };
+      print!("{}", StandardFullHelpWriter::new(ctx));
+    },
+    |program_name, err| {
+      let ctx = ErrorUsageWriterContext { options: &OPTIONS, program_name, error: err };
+      eprint!("{}", StandardErrorUsageWriter::new(ctx));
+    }
+  ) {
+    ParseMapResult::Map(map) => map,
+    ParseMapResult::ExitSuccess => { return ExitCode::SUCCESS; }
+    ParseMapResult::ExitFailure => { return ExitCode::FAILURE; }
+  };
+
+  println!("{:?}", map);
+  ExitCode::SUCCESS
+}