Problem with getting an item out of a list

Asked Feb 17 '19 at 18:16

Active Nov 09 '20 at 20:38

Viewed 70 times

Basically I have a list with elements with the following syntax:

name : value

(all are a symbol)

So now let's say that I have such an item in a list:

[price : '42']

Ideally using

 nth0(0, [price : '42'], X).

I'd expect X to be price : '42' .

Instead what I get is price:42 with the spaces removed.

Does anyone know why that is or maybe have a few pointers for doing this in a different manner?

(name : value must all be symbols)

edited Nov 09 '20 at 20:38

false

asked Feb 17 '19 at 18:16

Marco Grassi

2

You get `X = price:'42'.` as answer. Don't you? – false Feb 17 '19 at 18:19
`[price : 42]` is a list of one element. That element is the term, `:(price, 42)`. – lurker Feb 17 '19 at 18:20
This could probably be done using an [associative array in Prolog](https://stackoverflow.com/questions/53989755/associative-list-in-prolog). – Anderson Green Feb 17 '19 at 18:20
As an answer i get X = price:42 (without quotes). – Marco Grassi Feb 17 '19 at 18:23
2

try `X = price : '42', write_canonical(X), X =.. L, functor(X,F,A).` – Will Ness Feb 17 '19 at 18:29
If you do `X=price : '42', writeln(X)` it will print it without the quotes. that's just how it is written, not what it is. – Will Ness Feb 17 '19 at 19:11

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