Error Handling

ccalc provides MATLAB-compatible error handling so scripts can recover from runtime errors without crashing the session.

Raising errors

error('message')                   % plain message
error('expected %d, got %d', 2, n) % formatted (same as fprintf)
warning('result may be inaccurate') % prints to stderr, continues

try / catch / end

try
  result = risky_computation(x)
catch e
  fprintf('failed: %s\n', e.message)
  result = default_value
end

If the try body succeeds, catch is skipped.
catch e binds a struct with field message to the catch variable.
Anonymous catch (no variable) silently handles the error.
try with no catch silently swallows errors.

Inline fallback: `try(expr, default)`

n = try(str2num(s), 0)      % 0 if s is not a valid number
x = try(inv(A), eye(n))     % identity matrix if A is singular

The default is only evaluated if expr raises an error.

Protected call: `pcall`

[ok, val] = pcall(@func, arg1, arg2)
if ok
  % use val
else
  fprintf('error: %s\n', val)
end

Returns [1, result] on success and [0, message] on failure.

Last error message

lasterr()      % message from most recent error
lasterr('')    % clear

When a name is not found, ccalc compares it against all known variable names and built-in function names using edit distance. If a close match exists (at most 2 edits away), it is shown as a suggestion:

>> sqrtt(4)
Error: Unknown function 'sqrtt'; did you mean 'sqrt'?

>> my_valu + 1
Error: Undefined variable 'my_valu'; did you mean 'my_value'?

No suggestion is shown when no close match exists.

Source location in error messages

Errors inside block statements, function bodies, and scripts executed via run()/source() include a near line N suffix pointing to the failing line:

Error: Undefined variable: 'v' near line 3

The line number is 1-based and relative to the immediately enclosing block or function body, matching Octave’s convention.

When an error propagates through nested blocks the innermost location is kept — outer wrappers do not overwrite it. Inside a catch block, e.message contains the original message without the near line suffix.

See help errors for the full reference.

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