ParseError

The ParseError type provides structured error handling for parsing operations. Used by functions like Int.parse, Float.parse, and BigInt.parse.

import IO

match Int.parse "42"
  | Ok n -> println "Parsed: ${n}"
  | Err InvalidFormat{input} -> println "Invalid format: ${input}"
  | Err EmptyInput -> println "Empty input"
  | Err Overflow{input} -> println "Number too large: ${input}"

Constructors

ParseError

type ParseError = InvalidFormat{...} | EmptyInput | Overflow{...}

Constructor	Fields	Description
`InvalidFormat`	`input: String`	The input string has an invalid format for the target type
`EmptyInput`	—	The input string is empty
`Overflow`	`input: String`	The parsed value would overflow the target type

Trait Implementations

Show

Provides human-readable error descriptions:

err = InvalidFormat{input: "abc"}
println (show err)
# => InvalidFormat: abc

println (show EmptyInput)
# => EmptyInput

Error

Implements the standard Error trait with message and kind:

Constructor	Error Kind
`InvalidFormat`	`:invalid-format`
`EmptyInput`	`:empty-input`
`Overflow`	`:overflow`

Examples

Parsing User Input

parse-age = fn(input) =>
  match Int.parse (String.trim input)
    | Ok n if n >= 0 && n <= 150 -> Ok n
    | Ok n -> Err "Age must be between 0 and 150"
    | Err EmptyInput -> Err "Please enter an age"
    | Err InvalidFormat{..} -> Err "Please enter a valid number"
    | Err Overflow{..} -> Err "Number is too large"

Parsing with Default

parse-or-default = fn(input, default) =>
  match Int.parse input
    | Ok n -> n
    | Err _ -> default

port = parse-or-default (Env.get "PORT") 8080

Chaining Parse Operations

parse-point = fn(x-str, y-str) =>
  match (Int.parse x-str, Int.parse y-str)
    | (Ok x, Ok y) -> Ok {x: x, y: y}
    | (Err e, _) -> Err e
    | (_, Err e) -> Err e