Errors

 

   

The procedure error raises the exception  exn:user (which contains an error string). The error procedure can be invoked three ways:

• (error message) where message is a symbol. This creates a message string of the form ``error: message''.
• (error message value ) where message is a string. Theis creates a message string by concatenating message with string versions of the values (as printed by write). A space is inserted before each value.
• (error proc message value ) where proc is a symbol and message is a string. This creates a message string by evaluating

   
     (format (string-append "  s: " message) proc value   ) 
  

  (The built-in format and string-append are always used.)

The constructed message string is passed to make-exn:user and the resulting exception is raised.