Talk:Computer program: Difference between revisions

Revision as of 16:30, 28 November 2024

Revision as of 19:31, 8 February 2025

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== Correct results for Prolog numeric grade example ==

The displayed results for Prolog's numeric grade example is not what the user would expect. The article says the results will display: X = 'A'. The expected results should display: X = 4. [[User:Timhowardriley|TimhowardrileyUser:]] ([[User talk:Timhowardriley|talk]]) 19:59, 16 August 2023 (UTC)

:The example in its current form has two relations, which can be queried in isolation, or which can be queried in combination (like a join in a relational database). For example:

<syntaxhighlight lang="prolog">

numeric_grade('A', 4).

numeric_grade('B', 3).

numeric_grade('C', 2).

Line 71 ⟶ 69:

X = 'A',

Y = 4

</>

</syntaxhighlight>

:Alternatively, the query could be used to define a new relation, which gives the grade of a student as a number:

<syntaxhighlight lang="prolog">

numeric_grade('A', 4).

numeric_grade('B', 3).

numeric_grade('C', 2).

numeric_grade('D', 1).

numeric_grade('F', 0).

numeric_grade(X, -1) :- not X = 'A', not X = 'B', not X = 'C', not X = 'D', not X = 'F'.

grade_as_number(Student, Number) :-

Line 85 ⟶ 81:

?- grade_as_number('The Student', Number).

Number = 4

</syntaxhighlight> [[User:Robert Kowalski|Robert Kowalski]] ([[User talk:Robert Kowalski|talk]]) 08:18, 18Robert8 August 2023 (UTC)

Followup: It would be nice to learn Prolog's syntax for forming functions. Could this example be converted to a function? If so, then how would the the driver program execute it? [[User:Timhowardriley|Timhowardriley]] ([[User talk:Timhowardriley|talk]]) 20:33, 16 August 2023 (UTC)

Followup: It would be nice to learn Prolog's syntax for forming functions. Could this example be converted to a function? If so, then how would the the driver program execute it? [[User:Timhowardriley|Timhowardriley]] ([[User talk:Timhowardriley|talk]]) 20:33, 16 AugustexecuAugust 2023 (UTC)

: Here is the example in [[Ciao (programming language) | Ciao]] Prolog's functional syntax:

: Here is the example in [[Ciao (programming language) | Ciao]] Prolog's functional syntax:=

<syntaxhighlight lang="prolog">

numeric_grade('A') := 4.

numeric_grade('B') := 3.

numeric_grade('C') := 2.

numeric_grade('D') := 1.

numeric_grade('F') := 0.

numeric_grade(X) := -1 :- X \= 'A', X \= 'B', X \= 'C', X \= 'D', X \= 'F'.

grade_as_number(Student) := numeric_grade(grade(Student)).

grade('The Student') := 'A'.

Line 108 ⟶ 96:

Number = -1,

Student = bob

</>

</syntaxhighlight>

:Just for fun, the query asks for all input-output pairs that satisfy the functional relationship "grade_as_number". Good for debugging.