Captures only work when input is consumed

[sealmove]

I think this behavior is somewhat surprising.

let p = peg o:
  o <- >&1:
    echo len($1)

doAssert p.match("a").ok

0

Possible solutions:

• make it work
• produce a warning/error when > is used along with &
• mention it in the documentation

[zevv]

True, will document. Try instead:

let p = peg o:
  o <- &>1:
    echo len($1)

-- :wq ^X^Cy^K^X^C^C^C^C

[sealmove]

Unfortunately you snippet fails with:

Error: unhandled exception: Capture out of range, 1 is not in [0..0] [NPegException]

[zevv]

Sure, it needs this instead:

let p = peg o:
  o <- &p   
  p <- >1:
    echo len($1)

The reason is that & can have no side effects and internally restores the match state and all its captures to the state it was before. I'll add this to the documentation, thanks for reporting!