(
i * x u --
j * x )
Save the current input-source specification. Store
u in
BLK (thus making block
u the input source and
setting the input buffer to encompass its contents), set
>IN to zero, and interpret. When the parse area is
exhausted, restore the prior input source specification. Other
stack effects are due to the words
LOADed.
An ambiguous condition exists if
u is zero or is not a
valid block number.