Notes

LTAI Error Handling (4)

Context stack (with associated error messages)

Error look-up table

Error
Phrase
onlyOne There is only one value
noMore There is no more value
Empty The workspace is empty
NIL The value is nil
TooBig The result is too big
TooSmall The result is too small
NoValue There is no value in the workspace

Highest level error response: "I cannot <operation>, because <error>"

User asks "Why?" to progress down tree

At each node, the command is explained and an error given

User asks "Then?" to move onto the next right node to gain more information

System responds: "That is all." when tree search exhausted


Back to Teaching Support Page