I could add an "assert" function to lib/ur/top.ur
---
fun assert [a] (cond: bool) (msg: string) (loc: string) (x:a): a =
if cond then x else error <xml>{[msg]} at {[loc]}</xml>
---
Usage:
---
fun safeDivBy [a] (_:eq a) (_:num a) (loc:string) (denom: a) (n: a): a =
assert (denom <> zero) "precond: illegal divisor" loc <|
n `divide` denom
fun main (): transaction page =
let return <xml><body>{[result]}</body></xml>
where
val result = safeDivBy _LOC_ 0 5
end
----------------
BTW, "let ... where ... end" is not documented in the reference manual.
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