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[rustc.git] / src / libsyntax_ext / deriving / cmp / partial_ord.rs
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1// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
2// file at the top-level directory of this distribution and at
3// http://rust-lang.org/COPYRIGHT.
4//
5// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8// option. This file may not be copied, modified, or distributed
9// except according to those terms.
10
11pub use self::OrderingOp::*;
12
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13use deriving::generic::*;
14use deriving::generic::ty::*;
15
7453a54e 16use syntax::ast::{MetaItem, Expr, BinOpKind, self};
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17use syntax::codemap::Span;
18use syntax::ext::base::{ExtCtxt, Annotatable};
19use syntax::ext::build::AstBuilder;
20use syntax::parse::token::InternedString;
21use syntax::ptr::P;
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22
23pub fn expand_deriving_partial_ord(cx: &mut ExtCtxt,
24 span: Span,
25 mitem: &MetaItem,
62682a34 26 item: &Annotatable,
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27 push: &mut FnMut(Annotatable))
28{
29 macro_rules! md {
30 ($name:expr, $op:expr, $equal:expr) => { {
31 let inline = cx.meta_word(span, InternedString::new("inline"));
32 let attrs = vec!(cx.attribute(span, inline));
33 MethodDef {
34 name: $name,
35 generics: LifetimeBounds::empty(),
36 explicit_self: borrowed_explicit_self(),
37 args: vec!(borrowed_self()),
38 ret_ty: Literal(path_local!(bool)),
39 attributes: attrs,
62682a34 40 is_unsafe: false,
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41 combine_substructure: combine_substructure(Box::new(|cx, span, substr| {
42 cs_op($op, $equal, cx, span, substr)
43 }))
44 }
45 } }
46 }
47
48 let ordering_ty = Literal(path_std!(cx, core::cmp::Ordering));
49 let ret_ty = Literal(Path::new_(pathvec_std!(cx, core::option::Option),
50 None,
51 vec![Box::new(ordering_ty)],
52 true));
53
54 let inline = cx.meta_word(span, InternedString::new("inline"));
55 let attrs = vec!(cx.attribute(span, inline));
56
57 let partial_cmp_def = MethodDef {
58 name: "partial_cmp",
59 generics: LifetimeBounds::empty(),
60 explicit_self: borrowed_explicit_self(),
61 args: vec![borrowed_self()],
62 ret_ty: ret_ty,
63 attributes: attrs,
62682a34 64 is_unsafe: false,
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65 combine_substructure: combine_substructure(Box::new(|cx, span, substr| {
66 cs_partial_cmp(cx, span, substr)
67 }))
68 };
69
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70 // avoid defining extra methods if we can
71 // c-like enums, enums without any fields and structs without fields
72 // can safely define only `partial_cmp`.
73 let methods = if is_type_without_fields(item) {
74 vec![partial_cmp_def]
75 } else {
76 vec![
77 partial_cmp_def,
78 md!("lt", true, false),
79 md!("le", true, true),
80 md!("gt", false, false),
81 md!("ge", false, true)
82 ]
83 };
84
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85 let trait_def = TraitDef {
86 span: span,
87 attributes: vec![],
88 path: path_std!(cx, core::cmp::PartialOrd),
89 additional_bounds: vec![],
90 generics: LifetimeBounds::empty(),
e9174d1e 91 is_unsafe: false,
54a0048b 92 methods: methods,
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93 associated_types: Vec::new(),
94 };
62682a34 95 trait_def.expand(cx, mitem, item, push)
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96}
97
98#[derive(Copy, Clone)]
99pub enum OrderingOp {
100 PartialCmpOp, LtOp, LeOp, GtOp, GeOp,
101}
102
103pub fn some_ordering_collapsed(cx: &mut ExtCtxt,
104 span: Span,
105 op: OrderingOp,
106 self_arg_tags: &[ast::Ident]) -> P<ast::Expr> {
107 let lft = cx.expr_ident(span, self_arg_tags[0]);
108 let rgt = cx.expr_addr_of(span, cx.expr_ident(span, self_arg_tags[1]));
109 let op_str = match op {
110 PartialCmpOp => "partial_cmp",
111 LtOp => "lt", LeOp => "le",
112 GtOp => "gt", GeOp => "ge",
113 };
114 cx.expr_method_call(span, lft, cx.ident_of(op_str), vec![rgt])
115}
116
117pub fn cs_partial_cmp(cx: &mut ExtCtxt, span: Span,
118 substr: &Substructure) -> P<Expr> {
54a0048b 119 let test_id = cx.ident_of("__cmp");
d9579d0f 120 let ordering = cx.path_global(span,
e9174d1e 121 cx.std_path(&["cmp", "Ordering", "Equal"]));
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122 let ordering_expr = cx.expr_path(ordering.clone());
123 let equals_expr = cx.expr_some(span, ordering_expr);
d9579d0f 124
e9174d1e 125 let partial_cmp_path = cx.std_path(&["cmp", "PartialOrd", "partial_cmp"]);
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126
127 /*
128 Builds:
129
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130 match ::std::cmp::PartialOrd::partial_cmp(&self_field1, &other_field1) {
131 ::std::option::Option::Some(::std::cmp::Ordering::Equal) =>
132 match ::std::cmp::PartialOrd::partial_cmp(&self_field2, &other_field2) {
133 ::std::option::Option::Some(::std::cmp::Ordering::Equal) => {
134 ...
135 }
136 __cmp => __cmp
137 },
138 __cmp => __cmp
d9579d0f 139 }
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140 */
141 cs_fold(
142 // foldr nests the if-elses correctly, leaving the first field
143 // as the outermost one, and the last as the innermost.
144 false,
145 |cx, span, old, self_f, other_fs| {
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146 // match new {
147 // Some(::std::cmp::Ordering::Equal) => old,
148 // __cmp => __cmp
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149 // }
150
151 let new = {
152 let other_f = match (other_fs.len(), other_fs.get(0)) {
153 (1, Some(o_f)) => o_f,
154 _ => cx.span_bug(span, "not exactly 2 arguments in `derive(PartialOrd)`"),
155 };
156
157 let args = vec![
158 cx.expr_addr_of(span, self_f),
159 cx.expr_addr_of(span, other_f.clone()),
160 ];
161
162 cx.expr_call_global(span, partial_cmp_path.clone(), args)
163 };
164
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165 let eq_arm = cx.arm(span,
166 vec![cx.pat_some(span,
167 cx.pat_enum(span,
168 ordering.clone(),
169 vec![]))],
170 old);
171 let neq_arm = cx.arm(span,
172 vec![cx.pat_ident(span, test_id)],
173 cx.expr_ident(span, test_id));
174
175 cx.expr_match(span, new, vec![eq_arm, neq_arm])
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176 },
177 equals_expr.clone(),
178 Box::new(|cx, span, (self_args, tag_tuple), _non_self_args| {
179 if self_args.len() != 2 {
180 cx.span_bug(span, "not exactly 2 arguments in `derive(PartialOrd)`")
181 } else {
182 some_ordering_collapsed(cx, span, PartialCmpOp, tag_tuple)
183 }
184 }),
185 cx, span, substr)
186}
187
188/// Strict inequality.
189fn cs_op(less: bool, equal: bool, cx: &mut ExtCtxt,
190 span: Span, substr: &Substructure) -> P<Expr> {
7453a54e 191 let op = if less { BinOpKind::Lt } else { BinOpKind::Gt };
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192 cs_fold(
193 false, // need foldr,
194 |cx, span, subexpr, self_f, other_fs| {
195 /*
196 build up a series of chain ||'s and &&'s from the inside
197 out (hence foldr) to get lexical ordering, i.e. for op ==
198 `ast::lt`
199
200 ```
201 self.f1 < other.f1 || (!(other.f1 < self.f1) &&
202 (self.f2 < other.f2 || (!(other.f2 < self.f2) &&
203 (false)
204 ))
205 )
206 ```
207
208 The optimiser should remove the redundancy. We explicitly
209 get use the binops to avoid auto-deref dereferencing too many
210 layers of pointers, if the type includes pointers.
211 */
212 let other_f = match (other_fs.len(), other_fs.get(0)) {
213 (1, Some(o_f)) => o_f,
214 _ => cx.span_bug(span, "not exactly 2 arguments in `derive(PartialOrd)`")
215 };
216
217 let cmp = cx.expr_binary(span, op, self_f.clone(), other_f.clone());
218
7453a54e 219 let not_cmp = cx.expr_unary(span, ast::UnOp::Not,
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220 cx.expr_binary(span, op, other_f.clone(), self_f));
221
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222 let and = cx.expr_binary(span, BinOpKind::And, not_cmp, subexpr);
223 cx.expr_binary(span, BinOpKind::Or, cmp, and)
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224 },
225 cx.expr_bool(span, equal),
226 Box::new(|cx, span, (self_args, tag_tuple), _non_self_args| {
227 if self_args.len() != 2 {
228 cx.span_bug(span, "not exactly 2 arguments in `derive(PartialOrd)`")
229 } else {
230 let op = match (less, equal) {
231 (true, true) => LeOp, (true, false) => LtOp,
232 (false, true) => GeOp, (false, false) => GtOp,
233 };
234 some_ordering_collapsed(cx, span, op, tag_tuple)
235 }
236 }),
237 cx, span, substr)
238}