I'm a beginner with Prolog and there's a piece of code I've been trying to implement.
Essentially, you enter a string where the words inside the string are separated by spaces or exclamation marks or commas etc.
The string is returned as a list of strings with the words parsed out.
So for example, "stack,overflow!rocks." will return ["stack","overflow","rocks"]
I'd like to use swi prolog assoc or some map structure to look up the boundary characters but I can't figure it out.
I would be grateful for any help!
Those double quoted strings are really lists of character codes. Then a DCG is the appropriate way to handle the parsing:
:- use_module(library(http/dcg_basics), [string//1]).
%% split input on Sep
splitter(Sep, [Chunk|R]) -->
string(Chunk),
( Sep -> !, splitter(Sep, R)
; [], {R = []}
).
Sep above can be a literal, or a non terminal. We need something like
not_in_word --> [C], {\+code_type(C, alpha)}.
with such definitions:
?- phrase(splitter(not_in_word, X), "stack,overflow!rocks.").
X = [[115, 116, 97, 99, 107], [111, 118, 101, 114, 102, 108, 111|...], [114, 111, 99, 107, 115], []] .
We can get rid of the empty strings using delete/3:
?- phrase(splitter(not_in_word, X), "? stack,overflow!rocks."), delete(X, [], Y).
X = [[], [], [115, 116, 97, 99, 107], [111, 118, 101, 114, 102|...], [114, 111, 99, 107|...], []],
Y = [[115, 116, 97, 99, 107], [111, 118, 101, 114, 102, 108, 111|...], [114, 111, 99, 107, 115]] .
edit We can visualize the words easily as atoms:
?- phrase(splitter(not_in_word, X), "? stack,overflow!rocks."),
delete(X, [], Y),
maplist(atom_codes, Z, Y).
X = [[], [], [115, 116, 97, 99, 107], [111, 118, 101, 114, 102|...], [114, 111, 99, 107|...], []],
Y = [[115, 116, 97, 99, 107], [111, 118, 101, 114, 102, 108, 111|...], [114, 111, 99, 107, 115]],
Z = [stack, overflow, rocks] .
Note the 'output' words positions in maplist(atom_codes, Atoms, Codes)...
Related
Consider the following:
use sha2::{Sha256,Digest};
fn main() {
let mut hasher = Sha256::new();
hasher.update(b"hello world");
let result = hasher.finalize();
let str_result = format!("{:x}", result);
println!("A string is: {:x}", result);
println!("ASCII decimal maps: {:?}", str_result.bytes());
println!("What data coding is this?: {:?}", result);
}
The SHA256 hash as a string is: b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9
ASCII decimal maps: Bytes(Copied { it: Iter([98, 57, 52, 100, 50, 55, 98, 57, 57, 51, 52, 100, 51, 101, 48, 56, 97, 53, 50, 101, 53, 50, 100, 55, 100, 97, 55, 100, 97, 98, 102, 97, 99, 52, 56, 52, 101, 102, 101, 51, 55, 97, 53, 51, 56, 48, 101, 101, 57, 48, 56, 56, 102, 55, 97, 99, 101, 50, 101, 102, 99, 100, 101, 57]) })
What data coding is this?: [185, 77, 39, 185, 147, 77, 62, 8, 165, 46, 82, 215, 218, 125, 171, 250, 196, 132, 239, 227, 122, 83, 128, 238, 144, 136, 247, 172, 226, 239, 205, 233]
The first two make sense, we have the ASCII representations, followed by the ASCII > Decimal map. What is the third format? [185, 77, 39, 185, 147, 77, 62, 8, 165, 46, 82, 215, 218, 125, 171, 250, 196, 132, 239, 227, 122, 83, 128, 238, 144, 136, 247, 172, 226, 239, 205, 233]?
It's the bytes of the hash represented as an array of decimals instead of as a hexadecimal string.
b94d27... -> [185, 77, 39 ...]
0xb9 -> 185
0x4d -> 77
0x27 -> 39
I have this small program in rust, not in a cargo project.
use std::process::Command;
fn main() {
let result= Command::new("git").arg("status").output().expect("Ok");
println!("{:?}", result);
}
but after building and running it I get
Output { status: ExitStatus(unix_wait_status(0)), stdout: "On branch main\nYour branch is up to date with 'origin/main'.\n\nUntracked files:\n (use \"git add <file>...\" to include in what will be committed)\n\tbasics/guessing_game/\n\tcmdtest\n\tcmdtest.rs\n\nnothing added to commit but untracked files present (use \"git add\" to track)\n", stderr: "" }
If I try:
use std::process::Command;
fn main() {
let result= Command::new("git").arg("status").output().expect("Ok");
println!("{:?}", result.stdout);
}
I get
[79, 110, 32, 98, 114, 97, 110, 99, 104, 32, 109, 97, 105, 110, 10, 89, 111, 117, 114, 32, 98, 114, 97, 110, 99, 104, 32, 105, 115, 32, 117, 112, 32, 116, 111, 32, 100, 97, 116, 101, 32, 119, 105, 116, 104, 32, 39, 111, 114, 105, 103, 105, 110, 47, 109, 97, 105, 110, 39, 46, 10, 10, 85, 110, 116, 114, 97, 99, 107, 101, 100, 32, 102, 105, 108, 101, 115, 58, 10, 32, 32, 40, 117, 115, 101, 32, 34, 103, 105, 116, 32, 97, 100, 100, 32, 60, 102, 105, 108, 101, 62, 46, 46, 46, 34, 32, 116, 111, 32, 105, 110, 99, 108, 117, 100, 101, 32, 105, 110, 32, 119...
How can I print the string inside stdout and not numbers, in a user friendly format?
stdout may not be valid unicode, in which case you cannot print it. If you're sure it will be (which is probably the case with git), you can use String::from_utf8().unwrap():
fn main() {
let result = Command::new("git").arg("status").output().expect("Ok");
println!("{}", String::from_utf8(result.stdout).unwrap());
}
If you don't know, you can either check the Result from_utf8() returns, or use String::from_utf8_lossy() to turn invalid characters into U+FFFD REPLACEMENT CHARACTER �:
fn main() {
let result = Command::new("git").arg("status").output().expect("Ok");
println!("{}", String::from_utf8_lossy(&result.stdout));
}
I have parsed a file using lambda-multipart-parser and got results like this
and my code is
let result = await parser.parse(event);
let a= (result.files[0].content);
and o/p is
{
"type": "Buffer",
"data": [
65,
99,
99,
111,
117,
110,
116,
110,
117,
109,
98,
101,
114,
44,
85,
115,
101,
114,
110,
97,
109,
101,
44,
80,
97,
115,
115,
119,
111,
114,
100,
44,
76,
99,
111,
110,
97,
109,
101,
44,
83,
116,
97,
116,
117,
115 ]}
so to get data if i give
let a= (result.files[0].content.data);
I am getting output blank(i.e 1 in postman)
Even thought result.files[0].content is written out as a plain object, it is actually a Buffer object. So you'll have to use one of the methods on the object to retrieve the information, e.g., result.files[0].content.toString('utf-8') to get the UTF-8 string represented by the buffer.
I have a tuple (h) as follows:
(array([[145, 34, 26, 18, 90, 89],
[ 86, 141, 216, 167, 67, 214],
[ 18, 0, 212, 49, 232, 34],
...,
[147, 99, 73, 110, 108, 9],
[222, 133, 231, 48, 227, 154],
[184, 133, 169, 201, 162, 168]], dtype=uint8), array([[178, 58, 24, 90],
[ 3, 31, 129, 243],
[ 48, 92, 19, 108],
...,
[148, 21, 25, 209],
[189, 114, 46, 218],
[ 15, 43, 92, 61]], dtype=uint8), array([[ 17, 254, 216, ..., 126, 74, 129],
[231, 168, 214, ..., 131, 50, 107],
[ 77, 185, 229, ..., 86, 167, 61],
...,
[105, 240, 95, ..., 230, 158, 27],
[211, 46, 193, ..., 48, 57, 79],
[136, 126, 235, ..., 109, 33, 185]], dtype=uint8))
I converted it into a string s = str(h):
'(array([[ 1, 60, 249, 162, 51, 3],\n [ 57, 76, 193, 244, 17, 238],\n [ 22, 72, 101, 229, 185, 124],\n ...,\n [132, 243, 123, 192, 152, 107],\n [163, 187, 131, 47, 253, 155],\n [ 21, 3, 77, 208, 229, 15]], dtype=uint8), array([[119, 149, 215, 129],\n [146, 71, 121, 79],\n [114, 148, 121, 140],\n ...,\n [175, 121, 81, 71],\n [178, 92, 1, 99],\n [ 80, 122, 189, 209]], dtype=uint8), array([[ 26, 122, 248, ..., 104, 167, 29],\n [ 41, 213, 250, ..., 82, 71, 211],\n [ 20, 122, 4, ..., 152, 99, 121],\n ...,\n [133, 77, 84, ..., 238, 243, 240],\n [208, 183, 187, ..., 182, 51, 116],\n [ 19, 135, 48, ..., 210, 163, 58]], dtype=uint8))'
Now, I want to convert s back to a tuple. I tried using ast.literal_eval(s), but I get the following error:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3.5/ast.py", line 84, in literal_eval
return _convert(node_or_string)
File "/usr/lib/python3.5/ast.py", line 55, in _convert
return tuple(map(_convert, node.elts))
File "/usr/lib/python3.5/ast.py", line 83, in _convert
raise ValueError('malformed node or string: ' + repr(node))
ValueError: malformed node or string: <_ast.Call object at 0x76a6f770>
I could not find this exact solution anywhere. It would be great if someone could help me out.
You can't use str() on numpy arrays (wrapped in tuples or otherwise) and hope to recover the data.
First of all, the ast.literal_eval() function only supports literals and literal displays, not numpy array(...) syntax.
Next, str() on a tuple produces debugging-friendly output; tuples don't implement a __str__ string conversion hook, so their repr() representation is returned instead. Numpy arrays do support str() conversion, but their output is still but a friendly-looking string that omits a lot of detail from the actual values. In your example, those ... ellipsis dots indicate that there is more data in that part of the array, but the strings do not include those values. So you are losing data if you were to try to re-create your arrays from this.
If you need to store these tuples in a file or database column, or need to transmit them over a network connection, you need to serialise the data. Proper serialisation will preserve every detail of the arrays.
For tuples with numpy arrays, you can use pickle.dumps() to produce a bytes object that can be passed back to pickles.loads() to recreate the same value.
You can also convert invidual numpy arrays to a numpy-specific binary format, and load that format again, with the numpy.save() and numpy.load() functions (which operate directly on files, but you can pass in io.BytesIO() objects).
I am struggling with converting a Node application to Ruby. I have a Buffer of integers that I need to encode as an ASCII string.
In Node this is done like this:
const a = Buffer([53, 127, 241, 120, 57, 136, 112, 210, 162, 200, 111, 132, 46, 146, 210, 62, 133, 88, 80, 97, 58, 139, 234, 252, 246, 19, 191, 84, 30, 126, 248, 76])
const b = a.toString('hex')
// b = "357ff178398870d2a2c86f842e92d23e855850613a8beafcf613bf541e7ef84c"
const c = a.toString('ascii')
// c = '5qx9\bpR"Ho\u0004.\u0012R>\u0005XPa:\u000bj|v\u0013?T\u001e~xL'
I want to get the same output in Ruby but I don't know how to convert a to c. I used b to validate that a is parsed the same in Ruby and Node and it looks like it's working.
a = [53, 127, 241, 120, 57, 136, 112, 210, 162, 200, 111, 132, 46, 146, 210, 62, 133, 88, 80, 97, 58, 139, 234, 252, 246, 19, 191, 84, 30, 126, 248, 76].pack('C*')
b = a.unpack('H*')
# ["357ff178398870d2a2c86f842e92d23e855850613a8beafcf613bf541e7ef84c"]
# c = ???
I have tried serveral things, virtually all of the unpack options, and I also tried using the encode function but I lack the understanding of what the problem is here.
Okay well I am not that familiar with Node.js but you can get fairly close with some basic understandings:
Node states:
'ascii' - For 7-bit ASCII data only. This encoding is fast and will strip the high bit if set.
Update After rereading the nod.js description I think it just means it will drop 127 and only focus on the first 7 bits so this can be simplified to:
def node_js_ascii(bytes)
bytes.map {|b| b % 128 }
.reject(&127.method(:==))
.pack('C*')
.encode(Encoding::UTF_8)
end
node_js_ascii(a)
#=> #=> "5qx9\bpR\"Ho\u0004.\u0012R>\u0005XPa:\vj|v\u0013?T\u001E~xL"
Now the only differences are that node.js uses "\u000b" to represent a vertical tab and ruby uses "\v" and that ruby uses uppercase characters for unicode rather than lowercase ("\u001E" vs "\u001e") (you could handle this if you so chose)
Please note This form of encoding is not reversible due to the fact that you have characters that are greater than 8 bits in your byte array.
TL;DR (previous explanation and solution only works up to 8 bits)
Okay so we know the max supported decimal is 127 ("1111111".to_i(2)) and that node will strip the high bit if set meaning [I am assuming] 241 (an 8 bit number will become 113 if we strip the high bit)
With that understanding we can use:
a = [53, 127, 241, 120, 57, 136, 112, 210, 162, 200, 111, 132, 46, 146, 210, 62, 133, 88, 80, 97, 58, 139, 234, 252, 246, 19, 191, 84, 30, 126, 248, 76].map do |b|
b < 128 ? b : b - 128
end.pack('C*')
#=> "5\x7Fqx9\bpR\"Ho\x04.\x12R>\x05XPa:\vj|v\x13?T\x1E~xL"
Then we can encode that as UTF-8 like so:
a.encode(Encoding::UTF_8)
#=> "5\u007Fqx9\bpR\"Ho\u0004.\u0012R>\u0005XPa:\vj|v\u0013?T\u001E~xL"
but there is still is still an issue here.
It seems Node.js also ignores the Delete (127) when it converts to 'ascii' (I mean the high bit is set but if we strip it then it is 63 ("?") which doesn't match the output) so we can fix that too
a = [53, 127, 241, 120, 57, 136, 112, 210, 162, 200, 111, 132, 46, 146, 210, 62, 133, 88, 80, 97, 58, 139, 234, 252, 246, 19, 191, 84, 30, 126, 248, 76].map do |b|
b < 127 ? b : b - 128
end.pack('C*')
#=> "5\xFFqx9\bpR\"Ho\x04.\x12R>\x05XPa:\vj|v\x13?T\x1E~xL"
a.encode(Encoding::UTF_8, undef: :replace, replace: '')
#=> "5qx9\bpR\"Ho\u0004.\u0012R>\u0005XPa:\vj|v\u0013?T\u001E~xL"
Now since 127 - 128 = -1 (negative signed bit) becomes "\xFF" an undefined character in UTF-8 so we add undef: :replace what to do when the character is undefined use replace and we add replace: '' to replace with nothing.