Showing the boundary between accepted and rejected input is indeed a good idea. The case discussed in the article would benefit of a display with spaces betwee

Showing the boundary between accepted and rejected input is indeed a good idea. The case discussed in the article would benefit of a display with spaces between tokens. Example: Source: [01] Compiler error: [ 0 1 ] ----^ SyntaxError: JSON.parse: expected ‘,’ or ‘]’ after array element Such situation of two tokens without a separator character becomes much more obvious. Notice also the character showing point of error. OCaml has been doing for a while ( https://ocaml.org/learn/tutorials/common_error_messages.html https://ocaml.org/learn/tutorials/common_error_messages.html now shows underlined parts) then clang, cf. https://clang.llvm.org/diagnostics.html https://clang.llvm.org/diagnostics.html . This is much quicker for the human to communicate, than "line x column y".