Can anybody explain, why it is valid to read a number to add it to a another number, although reading just a number is not valid?
Prelude> read "5" + 3 8 Prelude> read "5" :33:1: No instance for (Read a0) arising from a use of `read' The type variable `a0' is ambiguous Possible fix: add a type signature that fixes these type variable(s) Note: there are several potential instances: instance Read () -- Defined in `GHC.Read' instance (Read a, Read b) => Read (a, b) -- Defined in `GHC.Read' instance (Read a, Read b, Read c) => Read (a, b, c) -- Defined in `GHC.Read' ...plus 25 others In the expression: read "5" In an equation for `it': it = read "5"
Why is "5" ambiguous?