auto merge of #12652 : rcxdude/rust/hexfloatext, r=alexcrichton

Closes #1433. Implemented after suggestion by @cmr in #12323

This is slightly less flexible than the implementation in #12323 (binary and octal floats aren't supported, nor are underscores in the literal), but is cleaner in that it doesn't modify the core grammar, or require odd syntax for the number itself. The missing features could be added back with relatively little effort (the main awkwardness is parsing the string. Is there a good approach for this in the stdlib currently?)

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);
+}