Problem with Unary minus

[jskolovos]

Hi, I have problems with a very simple grammar

# Filename: gram.ne

Expr   -> Sign Num
Sign   -> "+" | "-"
Num    -> Digit | Num Digit
Digit  -> [0-9]

I compiled it with

nearleyc ./gram.ne --out ./gram.js

and I tested it with nearley-test , I think the following output is incorrect

nearley-test ./gram.js --input '-1'

Table length: 1
Number of parses: 0
Parse Charts
Chart: 0
0: {Expr →  ● Sign Num}, from: 0
1: {Sign →  ● "+"}, from: 0
2: {Sign →  ● "-"}, from: 0

Parse results: 
[]

But with "+" sign instead of "-" it behaves as expected

nearley-test ./gram.js --input '+1'

Table length: 3
Number of parses: 1
Parse Charts
Chart: 0
0: {Expr →  ● Sign Num}, from: 0
1: {Sign →  ● "+"}, from: 0
2: {Sign →  ● "-"}, from: 0

Chart: 1
0: {Sign → "+" ● }, from: 0
1: {Expr → Sign ● Num}, from: 0
2: {Num →  ● Digit}, from: 1
3: {Num →  ● Num Digit}, from: 1
4: {Digit →  ● /[0-9]/}, from: 1

Chart: 2
0: {Digit → /[0-9]/ ● }, from: 1
1: {Num → Digit ● }, from: 1
2: {Num → Num ● Digit}, from: 1
3: {Expr → Sign Num ● }, from: 0
4: {Digit →  ● /[0-9]/}, from: 2

Parse results: 
[ [ [ '+' ], [ [ '1' ] ] ] ]

The nearley version I am using is:

nearleyc -v
2.19.4
nearley-test -v
2.19.4

I expected Parse results to be [ [ [ '-' ], [ [ '1' ] ] ] ] with the minus sign.

Is this a bug?? or am I missing something.

Thanks in advance.

[jskolovos]

Ok. After some tests, I have these findings.

It is a bug inside nearley-test.js, expecifically with commander.js

I put console.log('INP=', opts.input) before the instruction parser.feed(opts.input) in the sourcce code of nearley-test.js and when I test with nearley-test ./gg1.js --input '-1' it prints:

• INP= true

When I test with nearley-test ./gg1.js --input '+1' it prints:

• INP= +1

I'm glad nearley.js is not misbehaving, but I think it should be important to fix this problem in order to avoid other people facing this problem.

[kach]

Huh, that is odd. It seems the option parser thinks -1 is a flag.

To solve your immediate problem, can you pipe the input you want into nearley-test's stdin instead?

[jskolovos]

@kach Thanks for your reply.

I was worried that the problem where in the parser, but being in the tester, I can avoid making tests beginning with minus (they are only tests).

And when I put the parser in a program, I know it works just fine.

I think it is important to at least mention it in the docs, In order to help the people new into nearley.js.

Thanks again for the parser, the docs and examples.

[jskolovos]

I reopened this issue wondering somebody have something to add. Sorry for closing it before

[kach]

That's alright, I think it can be closed.