|<- <- -> ->|

Errors and Streams

e : [ f cmd, input, msg: (input[0], msg)' ^ \
      out 'OOPS: %s: %s' ]

– Error stream carries tuples containing (command, input, error message)

[...] groups a sequence of commands into a single command.

f 'cmd, input, msg: (input[0], msg) discards the command and extracts the first input.

– input and message are passed to 'OOPS: %s: %s' for formatting.