Pattern Matching

match.nim

# my alternative grammar is build around blocks as the most prominent syntax element:
# foo [anything]          means     foo do(anything):
#  ...                                ...
#
# foo                     is        foo:
#  ...                                ...
# 
# Then we have "match" magic/macro that looks like this:

match expr # The compiler automatically looks for a field used in a case
           # statement and matches against it
  nkSym [position typ] # Here the arguments are treated as variables that have to
                       # be unpacked from the matched value.
                       # Notice that you don't have to specify all of them
                       # it's also possible to extract "nested" values, but
                       # that's another story
    ...
  
  nkIdent [ident]
    ...

# example of a library defined deconstructor (regular expressions)
match str
  /(\w+)\s+(\d+)/ [word number]
    ...
    
# We could translate this in nimrod in something like this
# (with a bit more hacky transformations inside the macro):

match foo:
of nkSym(position, typ):
  ...
of nkIdent(ident):
  ...