Check String for numeric values

CheckNum

Create Function YourSchema/Checknum (Parstring Varchar(32))
       Returns Integer
   Language Sql
   Modifies Sql Data
   Deterministic
   Called On Null Input
   Secured
   Begin
     Declare LocNum  Decimal(31, 9) Not NUll Default 0;
     Declare Continue Handler For SQLException Return -1;
     
     Set LocNum = Cast(ParString as Dec(31, 9));
     Return 0;
   End;

Label On Routine YourSchema/Checknum(Varchar()) 
      Is 'Check Numeric Values';

Comment On Parameter Routine YourSchema/Checknum (Varchar())
       (Parstring Is 'String to be checked');
   
commit; 

/* Test */
With x (String) as (Values('12345'), ('-32,456'), ('0,23456'), ('-0,1000'), ('ABCD'), ('XYU'))
Select String, CheckNum(String) 
  from x;  

In case anyone gets an error when trying to create this function like I did:
The Secured attribute requires authority to Database Security Administrator Functions (QIBM_DB_SECADM).
Our system has the function usage for this as:
Default authority = *DENIED
*ALLOBJ specify authority = *NOTUSED
You have four options:

1. Comment out the Secured attribute.
2. Add yourself as an authorized user to the function usage. CHGFCNUSG FCNID(QIBM_DB_SECADM) USER(user-name) USAGE(*ALLOWED)
3. Change the default authority to *ALLOWED. CHGFCNUSG FCNID(QIBM_DB_SECADM) DEFAULT(*ALLOWED)
4. If you have *ALLOBJ authority, change the *ALLOBJ special authority to *USED. CHGFCNUSG FCNID(QIBM_DB_SECADM) ALLOBJAUT(*USED)