Skip to main content
Version: Next

with_context/2

Module​

This predicate is provided by error.pl.

Load this module before using the predicate:

:- consult('/v1/lib/error.pl').

Description​

Executes Goal and, if it throws a Prolog error term, rethrows the same formal error with Context as the error context.

Non-error exceptions are rethrown unchanged.

Signature​

with_context(+Context, :Goal) is det

Examples​

with_context/2 rewrites the error context of the wrapped goal​

This scenario demonstrates how with_context/2 preserves the formal error while replacing its context.

Here are the steps of the scenario:

  • Given the program:
  • Given the query:
consult('/v1/lib/error.pl'),
with_context(example/1, must_be(atom, 42)).
  • When the query is run
  • Then the answer we get is:
height: 42
gas_used: 4381
answer:
  has_more: false
  results:
  - error: "error(type_error(atom,42),example/1)"