Operations on lists
Operations on lists are of two types:
- Pair-wise -- Pair-wise operators act on two lists in parallel-element fashion. The first element of list 1 pairs with the first element of list 2, the second element of list 1 pairs with the second element of list 2, and so on. If one list has fewer elements than the other, the last element in the shorter list is repeated for operations with the remaining elements of the longer list. If list 1 consists of "A":"B":"C" and list 2 consists of "1":"2," the operation is performed as though list 2 contained "1":"2":"2." For pair-wise equality tests, only one match is needed for the statement to return True, or 1.
- Permuted -- Permutation operators act on two lists, pairing every possible combination of their values. The resulting list has an element for each pairing in the following order: list 1 element 1 paired with each element in list 2, list 1 element 2 paired with each element in list 2, and so on through the last element in list 1.
If an operation occurs on a list and a non-list value, the non-list value is paired with each element in the list.
The following table shows the pair-wise and permutation operators.
| Pair-wise operator |
Permutation operator |
Meaning |
|---|---|---|
| * |
** |
Multiplication |
| / |
*/ |
Division |
| + |
*+ |
Addition |
| - |
*- |
Subtraction |
| > |
*> |
Greater than |
| < |
*< |
Less than |
| >= |
*>= |
Greater than or equal to |
| <= |
*<= |
Less than or equal to |
| = |
*= |
Equal |
| != |
*!= |
Not equal |
The following table shows how pair-wise and permutation operators differ.
| Operation |
Statement |
Yields |
|---|---|---|
| Concatenation, pair-wise |
"A":"B":"C"+"1":"2":"3" "A":"B":"C"+"1":"2" "A":"B":"C"+"1" |
"A1":"B2":"C3" "A1":"B2":"C2" "A1":"B1":C1" |
| Concatenation, permutation |
"A":"B":"C"*+"1":"2":"3" "A":"B":"C"*+"1":"2" |
"A1":"A2":"A3":"B1":"B2":"B3":"C1":"C2":"C3" "A1":"A2":"B1":"B2":"C1":"C2" |
| Addition, pair-wise |
1:2:3+10:20:30 1:2:3+10:20 1:2:3+10 |
11:22:33 11:22:23 11:12:13 |
| Addition, permutation |
1:2:3*+10:20:30 1:2:3*+10:20 |
11:21:31:12:22:32:13:23:33 11:21:12:22:13:23 |
| Text equality, pair-wise |
"A":"B":"C"="B":"C":"A" "A":"B":"C"="B":"C" "B":"B":"C"="B":"C" |
0 False 1 True 1 |
| Text equality, permutation |
"A":"B":"C"*="B":"C":"A" "A":"B":"C"*="B":"C" "B":"B":"C"*="D":"E" |
1 1 0 |
| Number equality, pair-wise |
1:2:3=2:3:1 1:2:3=2:3 2:3:3=2:3 2:3:3=3:1 |
0 1 1 0 |
| Number equality, permutation |
1:2:3*=2:3:1 1:2:3*=2:3 1:2:3*=4:5 |
1 1 0 |
| Date equality, pair-wise |
[1-1-90]:[2-2-90]:[3-3-90]= [3-3-90]:[2-2-90]:[1-1-90] [1-1-90]:[2-2-90]:[3-3-90]= [2-2-90]:[3-3-90] [2-2-90]:[3-3-90]:[3-3-90]= [2-2-90]:[3-3-90] |
1 1 1 |
| Date equality, permutation |
[1-1-90]:[2-2-90]:[3-3-90]*= [3-3-90]:[2-2-90]:[1-1-90] [1-1-90]:[2-2-90]:[3-3-90]*= [2-2-90]:[3-3-90] [1-1-90]:[2-2-90]:[3-3-90]*= [4-4-90]:[5-5-90] |
1 1 0 |
Results
These rules can have surprising consequences. For example, it's possible for the expressions A=B and A!=B to both be true at the same time. For example, if A has the value 1:2 and B has the value 1:3. The pair 1 and 1 are compared, and 2 and 3 are compared. Because the first pair are equal, A=B is true. Because the second pair are not equal, A!=B is also true. When working with lists, the inverse of A=B is !(A=B).