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- OPT MODULE
-
- MODULE 'exec/nodes','exec/lists'
-
- EXPORT PROC isfirst(node:PTR TO ln)
- IF node.pred
- IF node.pred.pred=0 THEN RETURN TRUE
- ENDIF
- ENDPROC FALSE
-
- EXPORT PROC islast(node:PTR TO ln)
- IF node.succ
- IF node.succ.succ=0 THEN RETURN TRUE
- ENDIF
- ENDPROC FALSE
- EXPORT PROC ishead(node:PTR TO ln) IS IF (node.pred=0) THEN TRUE ELSE FALSE
- EXPORT PROC istail(node:PTR TO ln) IS IF (node.succ=0) THEN TRUE ELSE FALSE
-