CODEWITHSUNDEEP
prolog
Suzanne L.
Suzanne L.

Reputation: 115

Controlling parenthesis while working with operators

When working with user-defined operators, Prolog sometimes adds / removes parenthesis to expressions involving those operators automatically. Is there a way to control this?

Many thanks

Upvotes: 0

Views: 482

Answers (2)

Anniepoo
Anniepoo

Reputation: 2162

The parens are just added by portray. They're not part of the internal representation of the code. You can override portray to change how things are printed. see portray_text

Upvotes: 3

Daniel Lyons
Daniel Lyons

Reputation: 22803

An operator is defined like so:

:- op(Precedence, Associativity, Operator).

This answer to a similar question explains this, but the short answer is that the Associativity option controls this; xfy makes an operator left-associative and yfx makes an operator right associative. The Precedence tells Prolog how to decide which operator is the subexpression when it sees more than one.

Upvotes: 1

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