In Standard ML, it would be a type error to do that specifically: - if true then "abc" else 2.01; stdIn:1.2-1.30 Error: types of if branches do not agr

In Standard ML, it would be a type error to do that specifically: - if true then "abc" else 2.01; stdIn:1.2-1.30 Error: types of if branches do not agree [tycon mismatch] then branch: string else branch: real in expression: if true then "abc" else 2.01 You would need to define a new data type to wrap them: - datatype string_or_real = r of real | s of string; - if true then s "abc" else r 2.01; val it = s "abc" : string_or_real