Coming from PBASIC to Prop C: LookUp, LookDown
John Kauffman
Posts: 653
Does this seem right? It works but is there a better technique?
PBASIC
Prop C
Lookup: refer to the [element#] in the array
Lookdown: start with a value and get the index of the match in the array
PBASIC
LOOKUP IndexNumberIn,[item1,item2,item3], VarToReceiveValue LOOKDOWN ValueIn,[item1,item2,item3], VarToReceiveIndexNumber if item list is strings then: [item1,item2,item3]
Prop C
Lookup: refer to the [element#] in the array
char myResultHolder;
int myLookUpNumber = 2;
char myArrayOfLetters1[] = "abcd";
myResultHolder = myArrayOfLetters1[myLookUpNumber];
print("myLookUpNumber = 2 returned %c",myResultHolder);
Lookdown: start with a value and get the index of the match in the array
char myArrayOfLetters2[] = "wxyz";
char myLookUpValue = 'y';
int myResultIndexNumber;
int myArrayCounter;
for (myArrayCounter=0; myArrayCounter<sizeof(myArrayOfLetters2); myArrayCounter++){
if (myArrayOfLetters2[myArrayCounter] == myLookUpValue){
myResultIndexNumber=myArrayCounter;} //found
} // loop thorugh all members of array
print("myLookUpValue of 'y' returned index number of %d",myResultIndexNumber);
Comments
Lookdown: yes, a linear search. One small optimization is adding a "break;" if the item is found.
For the particular case of finding a letter in a string you can use the strchr function: http://www.cplusplus.com/reference/cstring/strchr/
if (myArrayOfLetters2[myArrayCounter] == myLookUpValue){ myResultIndexNumber=myArrayCounter; break;} //found } // loop through members of array until find a match