GV

GeezerVison

The World Wide Web, restored to 800 pixels of glory.

Home|About|Gaming cabinet|Archives|How it works|Starter sites

On this site

  • Sign in
  • ActionsCI/CD and automation
  • CodespacesCloud development environments
  • All Features
  • Documentation
  • Training
  • Certifications
  • Build with Copilot
  • Customize Copilot
  • Integrations
  • Trending repos
  • GitHub Sponsors
  • Developer articles
  • Enterprises

This view

  • Original page
  • New address

GeezerVison is showing github.com — tree-query/interp.d at main · CrazyPython/tree-query

Expand file tree

/

interp.d

Copy path
More file actions
More file actions

Latest commit

 

History

History
History
63 lines (62 loc) · 1.82 KB
/

interp.d

Copy path

File metadata and controls

63 lines (62 loc) · 1.82 KB
Raw
Copy raw file
Download raw file
Open symbols panel
Edit and raw actions
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
/+ A boolean expression interpreter.
+ Used to evaluate boolean bitfields for the query.
+/
module interp;
import std.variant;
import std.typecons;
// TCO
alias BitType = uint;
enum Op { AND, OR, NOT, ATOM };
bool eval_form(BitType bitstring, Form form) {
if (form.op == Op.AND) {
return eval_and(bitstring, form.operands);
} else if (form.op == Op.OR) {
return eval_or(bitstring, form.operands);
} else if (form.op == Op.NOT) {
return cast(bool)(!(bitstring & (1 << form.operands[0].bitshift)));
//return cast(bool)(!(bitstring & (1 << form.bitshift)));
} else {
return cast(bool)(bitstring & (1 << form.bitshift));
}
}
struct Form {
Op op;
union {
Form[] operands;
// What is faster, a ubyte or a byte?
ubyte bitshift;
}
}
bool eval_and(BitType bitstring, Form[] terms) {
if (terms.length == 0) {
return true;
}
if (eval_form(bitstring, terms[0])) {
return eval_and(bitstring, terms[1..$]);
} else {
// short-circuit evaluation
return false;
}
}
bool eval_or(BitType bitstring, Form[] terms) {
if (terms.length == 0) {
return false;
}
if (eval_form(bitstring, terms[0])) {
// short-circuit evaluation
return true;
} else {
return eval_or(bitstring, terms[1..$]);
}
}
private Form Atom(ubyte bitshift) {
Form form = { Op.ATOM, bitshift: bitshift };
return form;
}
unittest {
assert(eval_form(0b1, Form(Op.OR, [Atom(0)])) == true);
assert(eval_form(0b11, Form(Op.AND, [Atom(0), Atom(1)])) == true);
assert(eval_form(0b10, Form(Op.AND, [Atom(0), Atom(1)])) == false);
assert(eval_form(0b10, Form(Op.OR , [Atom(0), Atom(1)])) == true);
assert(eval_form(0b111,Form(Op.AND, [Form(Op.AND, [Atom(0), Atom(2)]), Atom(1)])) == true);
}
You are visitor 01402520 — GeezerVison does not store the pages you look up.
Best viewed with Netscape Navigator 4.7 or Internet Explorer 6 at 800×600. No cookies required.