Error Messages

Error messages by MINERVA:

• compiler errors:
  The compiler flags e.g. undefined predicates
• compiler warnings:
  The compiler flags suspected typos and violations of program laout conventions.
• run time MINERVA exceptions:
  The run time system maps errors into catchable exceptions. The program may deal with these exceptions explicitly.

Run time exceptions should be dealt with catch/3. Uncaught exceptions will ripple upwards.

In addition to error messages created by MINERVA. you may encounter error messages created by the underlying Java. Java errors can be caused by wrong file names, firewalls preventing access, incomplete installation of browsers or Java processors, and various bugs in the Java processors.

The following shows an example of minervac diagnostics including "hard" errors and heuristic warnings.

% MINERVA (c) IF Computer  1996,97
% http://www.ifcomputer.com/MINERVA   mailto:support@ifcomputer.com


% if you refer to a nonexisting package the compiler will complain.
% :- package(nonexisting).
% ** minerva compiler: error(existence_error(source_sink,'nonexisting.mpk'),
%    [goal = open('nonexisting.mpk',read,_291,[file,buffered,text])])


main(Args) :-
	a(missing),
	b(Lone),
	c.

% Variables are used to transport information.
% Subspect typo of variable name(s)
b(Variable) :- c(Var).

% This Variable is marked with '_'
b(_Variable) :- c.

% Predicates are in one place by convention.
% Suspect typo of predicate name.

c(whatever).
b(one_more).


% Predicates start in the first column by convention.
% Suspect e.g. ',' mistaken for '.'

d :-
	d1,
	d2.
	d3.

d1.
d2.
d3.

% And a couple of 'real' syntax violations.

err1 :- .
err2 :- err3(.
err4 :- err3).
err5 :- write([a,b,c,d).
err6 :- write((a,b,c,d])).

A is 5 is 7.

Here is the corresponding minervac error output:

minervac manyerrors
MINERVA 1.0 Development Server     http://www.ifcomputer.com/MINERVA
(c) IF Computer 1996,1997                 Licenced to ifcomputer.com

compile: manyerrors.min -> manyerrors.ass
*** syntax warning: singlevariable(Args)
>>> file = manyerrors.min, line = 11, column = 6
*** syntax warning: singlevariable(Lone)
>>> file = manyerrors.min, line = 13, column = 4
*** syntax warning: singlevariable(Variable)
>>> file = manyerrors.min, line = 18, column = 3
*** syntax warning: singlevariable(Var)
>>> file = manyerrors.min, line = 18, column = 18
*** compiler warning: discontiguous predicate: b / 1
*** syntax warning: term does not start at 1st column
>>> file = manyerrors.min, line = 36
*** compiler warning: discontiguous predicate: d3 / 0
*** syntax error: term expected, fullstop
>>> file = manyerrors.min, line = 44, column = 9
*** syntax error: term expected, fullstop
>>> file = manyerrors.min, line = 45, column = 14
*** syntax error: not in bracket-context, ')'
>>> file = manyerrors.min, line = 46, column = 13
*** syntax error: not in bracket-context, ')'
>>> file = manyerrors.min, line = 47, column = 23
*** syntax error: not in list-context, ']'
>>> file = manyerrors.min, line = 48, column = 23
*** syntax error: precedence error, is
>>> file = manyerrors.min, line = 50, column = 3
*** compiler error: undefined predicate: a / 1
*** compiler error: undefined predicate: c / 0