floats iter 4.6: codegen io/print_float + examples/floats.ail.json E2E fixture

crates/ailang-codegen/src/lib.rs

@@ -2294,6 +2294,28 @@ impl<'a> Emitter<'a> {
                 }
                 Ok(("0".into(), "i8".into()))
             }
+            "io/print_float" => {
+                if args.len() != 1 {
+                    return Err(CodegenError::Internal(
+                        "io/print_float arity".into(),
+                    ));
+                }
+                let (v, vty) = self.lower_term(&args[0])?;
+                if vty != "double" {
+                    return Err(CodegenError::Internal(
+                        "io/print_float needs double".into(),
+                    ));
+                }
+                let fmt = self.intern_string("fmt_float", "%g\n");
+                self.body.push_str(&format!(
+                    "  {call_kw} i32 (ptr, ...) @printf(ptr @{fmt}, double {v})\n"
+                ));
+                if tail {
+                    self.body.push_str("  ret i8 0\n");
+                    self.block_terminated = true;
+                }
+                Ok(("0".into(), "i8".into()))
+            }
             "io/print_str" => {
                 if args.len() != 1 {
                     return Err(CodegenError::Internal(
@@ -3269,4 +3291,43 @@ mod tests {
         assert!(ir.contains("0x7FF0000000000000"), "+inf bit pattern missing: {ir}");
         assert!(ir.contains("0xFFF0000000000000"), "-inf bit pattern missing: {ir}");
     }
+
+    /// Floats iter 4.6 RED: `(do io/print_float 1.5)` lowers via
+    /// `printf("%g\n", v)`, parallel to `io/print_int` at line 2152.
+    #[test]
+    fn lowers_io_print_float() {
+        use ailang_core::ast::*;
+        let body = Term::Do {
+            op: "io/print_float".into(),
+            args: vec![Term::Lit { lit: Literal::Float { bits: 0x3ff8_0000_0000_0000u64 } }],
+            tail: false,
+        };
+        let m = Module {
+            schema: ailang_core::SCHEMA.to_string(),
+            name: "t".into(),
+            imports: vec![],
+            defs: vec![Def::Fn(FnDef {
+                name: "main".into(),
+                ty: Type::Fn {
+                    params: vec![], ret: Box::new(Type::unit()), effects: vec!["IO".into()],
+                    param_modes: vec![], ret_mode: ParamMode::Implicit,
+                },
+                params: vec![], body, suppress: vec![], doc: None,
+            })],
+        };
+        let ir = emit_ir(&m).unwrap();
+        assert!(
+            ir.contains("call i32 (ptr, ...) @printf"),
+            "io/print_float not emitting printf: {ir}"
+        );
+        assert!(
+            ir.contains("double 0x3FF8000000000000"),
+            "Float arg not threaded through io/print_float: {ir}"
+        );
+        // Verify the format string `%g\n` is interned.
+        assert!(
+            ir.contains("%g") || ir.contains("\\67"), // `g` ASCII = 67 = 0x47
+            "format string `%g\\n` not interned: {ir}"
+        );
+    }
 }