is a global variable that, if set, is applied to any input string that is found to contain a syntax error.
- The arguments given to $SyntaxHandler are the complete input string and an integer specifying the character position at which the syntax error was detected.
- The first character in the string is taken to have position 1.
- Any string returned by $SyntaxHandler is used as a new version of the input string and is fed to the Wolfram Language. If the string does not end with a newline, the Wolfram Language waits for input to complete the line.
- If $SyntaxHandler returns $Failed, input to the Wolfram Language is abandoned if possible.
- Input is not assigned to InString[n] until after $SyntaxHandler is applied.
- $SyntaxHandler is not called for input from files obtained using Get.
Introduced in 1991