grab_example.grab

# assume that we'll be attaching to a dataset with 9 records,
# and that the 'records' in our dataset are [0,1,2,3,4,5,6,7,8]

# the Grab interpreter splits scripts into lines;
# any line that isn't an obvious instruction is ignored;
# all leading and trailing whitespace is stripped from every line;
# all characters on a line after an instruction has been recognized is ignored;
# instructions must be the first non-whitespace position of a line or the line is ignored

# running the script makes cumulative changes to a 'working subset' of the dataset,
#   which is a set of references to records in their canonical order

# 'all' appends a reference to every record in the attached dataset, in order
all     => [0,1,2,3,4,5,6,7,8]

# 'any' appends a reference to any one uniformly-sampled record
#   for example, 2 
any     => [0,1,2,3,4,5,6,7,8,2]

# a bare integer adds a reference to the record in that position in the dataset
#  NOTE: Grab is 0-based
1       => [0,1,2,3,4,5,6,7,8,2,1]

# integers are reduced modulo the number of records
#   for example, (52 % 9) = a reference to the record in position 7 of dataset
52      => [0,1,2,3,4,5,6,7,8,2,1,7]

# negative integers are also brought into range via modulo
#   for example, (-21 % 9) = a reference to the record in position 6 of dataset
-21     => [0,1,2,3,4,5,6,7,8,2,1,7,6]

# 'not \d' removes all references to records that are in a given position in the dataset
not 7   => [0,1,2,3,4,5,6,8,2,1,6]

# as before, the number is returned modulo the number of records in the original dataset
#   for example, (-7 % 9) = reference to record in position 2
not -7   => [0,1,3,4,5,6,8,1,6]

# 'not any' removes all local references to a random element of the attached dataset
#   for example, 6
not any  => [0,1,3,4,5,8,1]

# 'not all' removes all references to any record in the dataset
not all  => []

# the working subset is modified by each instruction in turn
any      => [5]
any      => [5,3]
all      => [5,3,0,1,2,3,4,5,6,7,8]
all      => [5,3,0,1,2,3,4,5,6,7,8,0,1,2,3,4,5,6,7,8]
not 5    => [3,0,1,2,3,4,6,7,8,0,1,2,3,4,6,7,8]