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1 | /* |
2 | * Licensed to the Apache Software Foundation (ASF) under one | |
3 | * or more contributor license agreements. See the NOTICE file | |
4 | * distributed with this work for additional information | |
5 | * regarding copyright ownership. The ASF licenses this file | |
6 | * to you under the Apache License, Version 2.0 (the | |
7 | * "License"); you may not use this file except in compliance | |
8 | * with the License. You may obtain a copy of the License at | |
9 | * | |
10 | * http://www.apache.org/licenses/LICENSE-2.0 | |
11 | * | |
12 | * Unless required by applicable law or agreed to in writing, | |
13 | * software distributed under the License is distributed on an | |
14 | * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | |
15 | * KIND, either express or implied. See the License for the | |
16 | * specific language governing permissions and limitations | |
17 | * under the License. | |
18 | */ | |
19 | ||
20 | module thrift.internal.ctfe; | |
21 | ||
22 | import std.conv : to; | |
23 | import std.traits; | |
24 | ||
25 | /* | |
26 | * Simple eager join() for strings, std.algorithm.join isn't CTFEable yet. | |
27 | */ | |
28 | string ctfeJoin(string[] strings, string separator = ", ") { | |
29 | string result; | |
30 | if (strings.length > 0) { | |
31 | result ~= strings[0]; | |
32 | foreach (s; strings[1..$]) { | |
33 | result ~= separator ~ s; | |
34 | } | |
35 | } | |
36 | return result; | |
37 | } | |
38 | ||
39 | /* | |
40 | * A very primitive to!string() implementation for floating point numbers that | |
41 | * is evaluatable at compile time. | |
42 | * | |
43 | * There is a wealth of problems associated with the algorithm used (e.g. 5.0 | |
44 | * prints as 4.999…, incorrect rounding, etc.), but a better alternative should | |
45 | * be included with the D standard library instead of implementing it here. | |
46 | */ | |
47 | string ctfeToString(T)(T val) if (isFloatingPoint!T) { | |
48 | if (val is T.nan) return "nan"; | |
49 | if (val is T.infinity) return "inf"; | |
50 | if (val is -T.infinity) return "-inf"; | |
51 | if (val is 0.0) return "0"; | |
52 | if (val is -0.0) return "-0"; | |
53 | ||
54 | auto b = val; | |
55 | ||
56 | string result; | |
57 | if (b < 0) { | |
58 | result ~= '-'; | |
59 | b *= -1; | |
60 | } | |
61 | ||
62 | short magnitude; | |
63 | while (b >= 10) { | |
64 | ++magnitude; | |
65 | b /= 10; | |
66 | } | |
67 | while (b < 1) { | |
68 | --magnitude; | |
69 | b *= 10; | |
70 | } | |
71 | ||
72 | foreach (i; 0 .. T.dig) { | |
73 | if (i == 1) result ~= '.'; | |
74 | ||
75 | auto first = cast(ubyte)b; | |
76 | result ~= to!string(first); | |
77 | ||
78 | b -= first; | |
79 | import std.math; | |
80 | if (b < pow(10.0, i - T.dig)) break; | |
81 | b *= 10; | |
82 | } | |
83 | ||
84 | if (magnitude != 0) result ~= "e" ~ to!string(magnitude); | |
85 | return result; | |
86 | } | |
87 | ||
88 | unittest { | |
89 | import std.algorithm; | |
90 | static assert(ctfeToString(double.infinity) == "inf"); | |
91 | static assert(ctfeToString(-double.infinity) == "-inf"); | |
92 | static assert(ctfeToString(double.nan) == "nan"); | |
93 | static assert(ctfeToString(0.0) == "0"); | |
94 | static assert(ctfeToString(-0.0) == "-0"); | |
95 | static assert(ctfeToString(2.5) == "2.5"); | |
96 | static assert(ctfeToString(3.1415).startsWith("3.141")); | |
97 | static assert(ctfeToString(2e-200) == "2e-200"); | |
98 | } |