Implement hexadecimal floating point literals via a syntax extension

closes rust-lang#1433

mk/crates.mk

@@ -51,7 +51,7 @@
 
 TARGET_CRATES := std extra green rustuv native flate arena glob term semver \
                  uuid serialize sync getopts collections num test time
-HOST_CRATES := syntax rustc rustdoc fourcc
+HOST_CRATES := syntax rustc rustdoc fourcc hexfloat
 CRATES := $(TARGET_CRATES) $(HOST_CRATES)
 TOOLS := compiletest rustdoc rustc
 
@@ -76,6 +76,7 @@ DEPS_sync := std
 DEPS_getopts := std
 DEPS_collections := std
 DEPS_fourcc := syntax std
+DEPS_hexfloat := syntax std
 DEPS_num := std
 DEPS_test := std extra collections getopts serialize term
 DEPS_time := std serialize

src/libhexfloat/lib.rs

@@ -0,0 +1,178 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/*!
+Syntax extension to create floating point literals from hexadecimal strings
+
+Once loaded, hexfloat!() is called with a string containing the hexadecimal
+floating-point literal, and an optional type (f32 or f64).
+If the type is omitted, the literal is treated the same as a normal unsuffixed
+literal.
+
+# Examples
+
+To load the extension and use it:
+
+```rust,ignore
+#[phase(syntax)]
+extern crate hexfloat;
+
+fn main() {
+    let val = hexfloat!("0x1.ffffb4", f32);
+}
+ ```
+
+# References
+
+* [ExploringBinary: hexadecimal floating point constants]
+  (http://www.exploringbinary.com/hexadecimal-floating-point-constants/)
+
+*/
+
+#[crate_id = "hexfloat#0.10-pre"];
+#[crate_type = "rlib"];
+#[crate_type = "dylib"];
+#[license = "MIT/ASL2"];
+
+#[feature(macro_registrar, managed_boxes)];
+
+extern crate syntax;
+
+use syntax::ast;
+use syntax::ast::Name;
+use syntax::codemap::{Span, mk_sp};
+use syntax::ext::base;
+use syntax::ext::base::{SyntaxExtension, BasicMacroExpander, NormalTT, ExtCtxt, MRExpr};
+use syntax::ext::build::AstBuilder;
+use syntax::parse;
+use syntax::parse::token;
+
+#[macro_registrar]
+pub fn macro_registrar(register: |Name, SyntaxExtension|) {
+    register(token::intern("hexfloat"),
+        NormalTT(~BasicMacroExpander {
+            expander: expand_syntax_ext,
+            span: None,
+        },
+        None));
+}
+
+//Check if the literal is valid (as LLVM expects),
+//and return a descriptive error if not.
+fn hex_float_lit_err(s: &str) -> Option<(uint, ~str)> {
+    let mut chars = s.chars().peekable();
+    let mut i = 0;
+    if chars.peek() == Some(&'-') { chars.next(); i+= 1 }
+    if chars.next() != Some('0') { return Some((i, ~"Expected '0'")); } i+=1;
+    if chars.next() != Some('x') { return Some((i, ~"Expected 'x'")); } i+=1;
+    let mut d_len = 0;
+    for _ in chars.take_while(|c| c.is_digit_radix(16)) { chars.next(); i+=1; d_len += 1;}
+    if chars.next() != Some('.') { return Some((i, ~"Expected '.'")); } i+=1;
+    let mut f_len = 0;
+    for _ in chars.take_while(|c| c.is_digit_radix(16)) { chars.next(); i+=1; f_len += 1;}
+    if d_len == 0 && f_len == 0 {
+        return Some((i, ~"Expected digits before or after decimal point"));
+    }
+    if chars.next() != Some('p') { return Some((i, ~"Expected 'p'")); } i+=1;
+    if chars.peek() == Some(&'-') { chars.next(); i+= 1 }
+    let mut e_len = 0;
+    for _ in chars.take_while(|c| c.is_digit()) { chars.next(); i+=1; e_len += 1}
+    if e_len == 0 {
+        return Some((i, ~"Expected exponent digits"));
+    }
+    match chars.next() {
+        None => None,
+        Some(_) => Some((i, ~"Expected end of string"))
+    }
+}
+
+pub fn expand_syntax_ext(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree]) -> base::MacResult {
+    let (expr, ty_lit) = parse_tts(cx, tts);
+
+    let ty = match ty_lit {
+        None => None,
+        Some(Ident{ident, span}) => match token::get_ident(ident).get() {
+            "f32" => Some(ast::TyF32),
+            "f64" => Some(ast::TyF64),
+            _ => {
+                cx.span_err(span, "invalid floating point type in hexfloat!");
+                None
+            }
+        }
+    };
+
+    let s = match expr.node {
+        // expression is a literal
+        ast::ExprLit(lit) => match lit.node {
+            // string literal
+            ast::LitStr(ref s, _) => {
+                s.clone()
+            }
+            _ => {
+                cx.span_err(expr.span, "unsupported literal in hexfloat!");
+                return base::MacResult::dummy_expr(sp);
+            }
+        },
+        _ => {
+            cx.span_err(expr.span, "non-literal in hexfloat!");
+            return base::MacResult::dummy_expr(sp);
+        }
+    };
+
+    {
+        let err = hex_float_lit_err(s.get());
+        match err {
+            Some((err_pos, err_str)) => {
+                let pos = expr.span.lo + syntax::codemap::Pos::from_uint(err_pos + 1);
+                let span = syntax::codemap::mk_sp(pos,pos);
+                cx.span_err(span, format!("invalid hex float literal in hexfloat!: {}", err_str));
+                return base::MacResult::dummy_expr(sp);
+            }
+            _ => ()
+        }
+    }
+
+    let lit = match ty {
+        None => ast::LitFloatUnsuffixed(s),
+        Some (ty) => ast::LitFloat(s, ty)
+    };
+    MRExpr(cx.expr_lit(sp, lit))
+}
+
+struct Ident {
+    ident: ast::Ident,
+    span: Span
+}
+
+fn parse_tts(cx: &ExtCtxt, tts: &[ast::TokenTree]) -> (@ast::Expr, Option<Ident>) {
+    let p = &mut parse::new_parser_from_tts(cx.parse_sess(),
+                                            cx.cfg(),
+                                            tts.iter()
+                                               .map(|x| (*x).clone())
+                                               .collect());
+    let ex = p.parse_expr();
+    let id = if p.token == token::EOF {
+        None
+    } else {
+        p.expect(&token::COMMA);
+        let lo = p.span.lo;
+        let ident = p.parse_ident();
+        let hi = p.last_span.hi;
+        Some(Ident{ident: ident, span: mk_sp(lo, hi)})
+    };
+    if p.token != token::EOF {
+        p.unexpected();
+    }
+    (ex, id)
+}
+
+// FIXME (10872): This is required to prevent an LLVM assert on Windows
+#[test]
+fn dummy_test() { }

src/test/compile-fail/syntax-extension-hexfloat-bad-lits.rs

@@ -0,0 +1,35 @@
+// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-stage1
+// ignore-pretty
+// ignore-cross-compile #12102
+
+#[feature(phase)];
+
+#[phase(syntax)]
+extern crate hexfloat;
+
+fn main() {
+    hexfloat!("foo");
+    //~^ ERROR invalid hex float literal in hexfloat!: Expected '0'
+    hexfloat!("0");
+    //~^ERROR invalid hex float literal in hexfloat!: Expected 'x'
+    hexfloat!("0x");
+    //~^ERROR invalid hex float literal in hexfloat!: Expected '.'
+    hexfloat!("0x.");
+    //~^ERROR invalid hex float literal in hexfloat!: Expected digits before or after decimal point
+    hexfloat!("0x0.0");
+    //~^ERROR invalid hex float literal in hexfloat!: Expected 'p'
+    hexfloat!("0x0.0p");
+    //~^ERROR invalid hex float literal in hexfloat!: Expected exponent digits
+    hexfloat!("0x0.0p0f");
+    //~^ERROR invalid hex float literal in hexfloat!: Expected end of string
+}

src/test/compile-fail/syntax-extension-hexfloat-bad-types.rs

@@ -0,0 +1,27 @@
+// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-stage1
+// ignore-pretty
+// ignore-cross-compile #12102
+
+#[feature(phase)];
+
+#[phase(syntax)]
+extern crate hexfloat;
+
+fn main() {
+    hexfloat!(foo);
+    //~^ ERROR non-literal in hexfloat!
+    hexfloat!(0);
+    //~^ ERROR unsupported literal in hexfloat!
+    hexfloat!("0x0.p0", invalid);
+    //~^ ERROR invalid floating point type in hexfloat!
+}

src/test/run-pass/syntax-extension-hexfloat.rs

@@ -0,0 +1,31 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-stage1
+// ignore-pretty
+// ignore-cross-compile #12102
+// ignore-fast
+
+#[feature(phase)];
+#[phase(syntax)]
+extern crate hexfloat;
+
+pub fn main() {
+    let a = hexfloat!("0x1.999999999999ap-4");
+    assert_eq!(a, 0.1);
+    let b = hexfloat!("-0x1.fffp-4", f32);
+    assert_eq!(b, -0.12498474_f32);
+    let c = hexfloat!("0x.12345p5", f64);
+    let d = hexfloat!("0x0.12345p5", f64);
+    assert_eq!(c,d);
+    let f = hexfloat!("0x10.p4", f32);
+    let g = hexfloat!("0x10.0p4", f32);
+    assert_eq!(f,g);
+}