New Issue: I/O module: adjustments to read methods

19498, "mppf", "I/O module: adjustments to read methods", "2022-03-18T15:19:23Z"

proc args...) : bool throws
proc t) : t throws
proc t...) : tuple throws
  • In [#18496] discussed if we want both type and return-through-argument versions
    • Seems that we want both forms because return-through-argument can return bool & is easier for loops
  • ‘read(string)’ today just reads one word but that’s a common stumbling block [#7952, #15844]
  • ‘read(myClass)’ fails if ‘myClass’ is ‘nil’ but arguably should allocate a class [#7950]


  • Keep both type and non-type forms
  • Use ‘out’ instead of ‘ref’ (requires also moving away from ‘ioLiteral’ and ‘ioNewline’) & allocate class instances
  • With the default Decoder:
    • ‘read(string)’ or ‘read(myString)’ should read until EOF and same for bytes
    • (works with the default Encoder where e.g. ‘write(“Hello World”)’ will not output quotes)
    • a read call containing a string as anything other than the last argument will throw
proc args..., decoder=reader.decoder()) : bool throws
proc t, decoder=reader.decoder()) : t throws
proc t..., decoder=reader.decoder()) : tuple throws
  • The ‘out’ version will return ‘false’ and default initialize the arguments if it reached EOF
  • It will produce a compilation error if any argument type is not default initializeable
  • It will return ‘true’ for success or throw if there was an error, including a partial read before EOF
  • The ‘type t’ version will throw if it reaches EOF