Simple code question

Using Arduino Programming Questions
1

real noob here trying to figure out a sketch

can someone explain "if (isnan (c))"

Thanks

2

Hard without any other context but isnan looks like a function that takes in a variable c and returns a Boolean variable.

3

Is Not A Number
is how I would interpret it.
Some floating point values are not valid, so are described as NaN

Of course, more context would make things clearer.

4

googling for arduino isnan brought me here:

5

Absolute noob here - I am having difficulty getting a LCD to operate with a thermocouple. A sketch for the serial works fine but with the LCD I get the message after the "if" condition. If I knew what that was, I might be able to figure out why the LCD is not working properly - seems to be hooked up to the UNO okay since "Hello, world!" works fine

The "if" condition is about 12 lines from the bottom.

The thermocouple is connected to a MAX TC amp from Adafruit. It all works fine with the serial monitor.

#include "Adafruit_MAX31855.h"
#include <LiquidCrystal.h>

int thermoCLK = 3;
int thermoCS = 4;
int thermoDO = 5;

// Initialize the Thermocouple
Adafruit_MAX31855 thermocouple(thermoCLK, thermoCS, thermoDO);
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(11,12,7,8,9,10);

  
void setup() {
  Serial.begin(9600);
  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);
  
  lcd.print("MAX31855 test");
  // wait for MAX chip to stabilize
  delay(500);
}

void loop() {
  // basic readout test, just print the current temp
   lcd.setCursor(0, 0);
   lcd.print("Int. Temp = ");
   lcd.print(thermocouple.readInternal());
  
   lcd.print("  "); 
     
   double c = thermocouple.readCelsius();
   lcd.setCursor(0, 1);
   if (isnan(c)) 
   {
     lcd.print("T/C Problem");
   } 
   else 
   {
     lcd.print("C = "); 
     lcd.print(c);
     lcd.print("  "); 
   }
 
   delay(1000);
}
6

I'd probably print the value of "c" in hex, cast to an "unsigned long".

if (isnan(c)) 
   {
     Serial.print((unsigned long) c, HEX);
   }
7

Regarding isnan(): std::isnan - cppreference.com

Does the liquidCrystal support printing floats? The reference page suggests it does not:

8

AWOL:
I'd probably print the value of "c" in hex, cast to an "unsigned long".

if (isnan(c))

{
     Serial.print((unsigned long) c, HEX);
   }

If c is not a number, is it really a good idea to print a number? Why not:

if (isnan(c)) 
   {
     Serial.print("NaN");
   }

although the Print class already does this check.

9

If c is not a number, is it really a good idea to print a number? W

I'm just curious to see which particular NaN pattern has been chosen.
I did say it was a personal thing.