diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 37 |
1 files changed, 36 insertions, 1 deletions
@@ -34367,7 +34367,42 @@ cell, then .code iter-step returns the .code cdr -field of that cell. +field of that cell. That value must itself be a +.code cons +or else +.codn nil , +otherwise an error is thrown. This is to prevent iteration +from wrongly iterating into the non-null terminators of improper +lists. Without this rule, iteration of a list like +.code "(1 2 . 3)" +would reach the +.code cons +cell +.code "(2 . 3)" +at which point a subsequent +.code iter-step +would return the +.code cdr +field +.codn 3 . +But that value is a valid iterator which will then continue by +stepping through +.codn 4 , +.code 5 +and so on. + +If +.meta iter +is a list-like sequence, then +.code cdr +is invoked on it and that value is returned. +The value must also be a list-like sequence, or else +.codn nil . +The reasoning for this is the same as for the similar +restriction imposed in the case when +.meta iter +is a +.codn cons . If .meta iter |