Found this one again after reading Discourse https://octave.discourse.group/t/please-add-closing-parenthesis/386

A patch has been submitted 2018 by Sudeepam to GitHub:

https://github.com/Sudeepam97/Correction_suggestion

Sorry, that it has not been applied yet.  Despite the patch needs a freshening up (it does not apply cleanly to the default branch) are there any reasons not to apply it for Octave 7?

Hi everyone,

This is Shane here from Octave Online.  I shared with Sudeepam a number of Octave Online sessions from late 2017 that shows the command a user entered, the error message, and the command that the user followed up with.  Here are some examples:

==========
cmd: Sqrt(4)
err: error: 'Sqrt' undefined near line 1 column 1
err:
cmd: sqrt(4)
==========
cmd: grod
err: error: 'grod' undefined near line 1 column 1
err:
cmd: grid
==========
cmd: titel('m');
err: error: 'titel' undefined near line 1 column 1
err:
cmd: title('m');
==========
cmd: lc
err: error: 'lc' undefined near line 1 column 1
err:
cmd: clc
==========

Based on looking through many of these sessions, the many various different ways of spelling "clc" seem to top the list for the most often misspelled token.

I got some really cool idea.
As soon as some mentor will be decided I will start working for this.Please do this quick.

Haven't written one up or even seen one before, but I can take a look at it thus weekend. Assuming there are models on the gsoc wiki page. If not point me in the right direction. As far as mentoring if simeone picks it up though, would probably need someone who knows more of the back end of the interpreter/GUI.

i was curious. a few trials did not produce the 'did you mean' response until the command had >=5 characters. Arcsin(1) did suggest asin(1),but arcsec(1) didn't suggest asec(1).

Regarding multiple possibilities, various misspellings of interp, interp1, interp2, interpn, etc., failed to invoke the 'did you mean'. 

so I'm guessing there's just a lookup table involved with frequent misspellings. (maybe matlab logs and reports back such things?). But, this is one of those areas where Octave isn't bounded by Matlab behavior, so it could be an interesting area for improvement.

For how to handle things, Matlab immediately places the suggested command on the interpreter line, such that you hit enter and it executes. So that precludes multiple options. I guess you could try presenting the options in a bash tab-completion sort of way (a la the show-all-if-ambiguous option)

This could quickly get quite involved. Maybe it should go on a GSOC project suggestion?

Yes, I have been thinking that it would be nice to have something like Matlab's "Did you mean" prompts.

What types of "close" should be included?  Possibilities are:
1. one-letter substitution (including digits and underline)
2. one-letter addition
3. one-letter deletion
4. transposition of adjacent letters

We should probably not do this for very short identifiers.  Would 4 characters be a suitable minimum?

I assume the reference list would be the list of ~2000 returned by pressing "<TAB>" at the start of a word.  Unfortunately, preprocessing couldn't be cached, because that list contains the variables in the current scope, but this is in the slow path anyway.

What should we do if there is more than one replacement?  The enthusiastic option would be to prioritise "likely" ones (such as ...our->...or/...ise->...ize, adjacent on the keyboard, vowel-to-vowel replacement).  Alternative approaches would be to list all of them, suggest the first one found, or do nothing.

(Although I think this is a great idea, could someone please reduce the severity and priority of this bug?)

Example: error: 'rgb2grey' undefined near line 1 column 1. Did you mean 'rgb2gray' (U.S. spelling)?

instead of:

error: 'rgb2grey' undefined near line 1 column 1

R treats the two as synonyms, but obviously that would harm Matlab compatibility. Color/colour might also be useful.

The example is from the "image" package, but applicability is wider.