Function kdbplus::api::is_error

pub fn is_error(catched: K) -> bool

Judge if a catched object by error_to_string is a genuine error object of type qtype::ERROR (This means false positive of the KNULL case can be eliminated).

Examples

use kdbplus::*;
use kdbplus::api::*;

fn love_even(arg: K) -> K{
  if let Ok(int) = arg.get_int(){
    if int % 2 == 0{
      // Silent for even value
      KNULL
    }
    else{
      // Shout against odd value
      new_error("great is the even value!!\0")
    }
  }
  else{
    // Pass through
    increment_reference_count(arg)
  }
}

#[no_mangle]
pub extern "C" fn propagate(arg: K) -> K{
  let result=error_to_string(love_even(arg));
  if is_error(result){
    // Propagate the error
    result
  }
  else if result.get_type() == qtype::ERROR{
    // KNULL
    println!("this is KNULL");
    decrement_reference_count(result);
    KNULL
  }
  else{
    // Other
    new_symbol("sonomama")
  }
}

q)convey: `libapi_examples 2: (`propagate; 1);
q)convey[7i]
'great is the even value!!
q)convey[12i]
this is KNULL
q)convey[5.5]
`sonomama

Note

In this example KNULL is used as a returned value of the function called by another function to demonstrate how is_error works. However, KNULL should not be used in such a way in order to avoid this kind of complexity. To return a general null for inner functions, use new_null instead.