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# Unsigned integer subtraction

## Problem

You want to perform subtraction where the result is unsigned and never negative.

## Solution

When a subtraction result would be negative, the answer should be zero. The following query creates a UDF that performs the calculation:

``````client.query(
q.CreateFunction({
name: 'subtract_unsigned',
body: q.Query(
q.Lambda(
['a', 'b'],
q.Let(
{
diff: q.Subtract(q.Var('a'), q.Var('b')),
negative: q.Not(q.Equals(q.Var('diff'), q.Abs(q.Var('diff')))),
},
q.If(q.Var('negative'), 0, q.Var('diff'))
)
)
),
})
)
.then((ret) => console.log(ret))
.catch((err) => console.error(
'Error: [%s] %s: %s',
err.name,
err.message,
err.errors()[0].description,
))``````
``````result = client.query(
q.create_function({
"name": "subtract_unsigned",
"body": q.query(
q.lambda_(
["a", "b"],
q.let(
{
"diff": q.subtract(q.var("a"), q.var("b")),
"negative": q.not_(q.equals(q.var("diff"), q.abs(q.var("diff"))))
},
q.if_(q.var("negative"), 0, q.var("diff"))
)
)
)
})
)
print(result)``````
``````result, err := client.Query(
f.CreateFunction(
f.Obj{
"name": "subtract_unsigned",
"body": f.Query(
f.Lambda(
f.Arr{"a", "b"},
f.Let().Bind(
"diff", f.Subtract(f.Var("a"), f.Var("b")),
).Bind(
"negative", f.Not(
f.Equals(f.Var("diff"), f.Abs(f.Var("diff"))),
),
).In(
f.If(f.Var("negative"), 0, f.Var("diff")),
),
),
),
},
))

if err != nil {
fmt.Fprintln(os.Stderr, err)
} else {
fmt.Println(result)
}``````
``````try
{
Value result = await client.Query(
CreateFunction(
Obj(
"name", "subtract_unsigned",
"body", Query(
Lambda(
Arr("a", "b"),
Let(
"diff", Subtract(Var("a"), Var("b")),
"negative", Not(
EqualsFn(Var("diff"), Abs(Var("diff")))
)
).In(
If(Var("negative"), 0, Var("diff"))
)
)
)
)
)
);
Console.WriteLine(result);
}
catch (Exception e)
{
Console.WriteLine(\$"ERROR: {e.Message}");
}``````
``````CreateFunction({
name: "subtract_unsigned",
body: Query(
Lambda(
["a", "b"],
Let(
{
diff: Subtract(Var("a"), Var("b")),
negative: Not(Equals(Var("diff"), Abs(Var("diff"))))
},
If(Var("negative"), 0, Var("diff"))
)
)
)
})``````
Query metrics:
•    bytesIn:  296

•   bytesOut:  398

• computeOps:    1

•   writeOps:    1

• writeBytes:  504

•  queryTime: 37ms

•    retries:    0

The following query calls the UDF with parameters that return a positive result:

``````client.query(
q.Call('subtract_unsigned', 123, 45)
)
.then((ret) => console.log(ret))
.catch((err) => console.error(
'Error: [%s] %s: %s',
err.name,
err.message,
err.errors()[0].description,
))``````
``78``
``````result = client.query(
q.call("subtract_unsigned", 123, 45)
)
print(result)``````
``78``
``````result, err := client.Query(
f.Call("subtract_unsigned", 123, 45))

if err != nil {
fmt.Fprintln(os.Stderr, err)
} else {
fmt.Println(result)
}``````
``78``
``````try
{
Value result = await client.Query(
Call("subtract_unsigned", 123, 45)
);
Console.WriteLine(result);
}
catch (Exception e)
{
Console.WriteLine(\$"ERROR: {e.Message}");
}``````
``LongV(78)``
``Call("subtract_unsigned", 123, 45)``
``78``
Query metrics:
•    bytesIn:  49

•   bytesOut:  15

• computeOps:   1

•   writeOps:   0

• writeBytes:   0

•  queryTime: 9ms

•    retries:   0

The following query calls the UDF with parameters that return what would have been a negative result:

``````client.query(
q.Call('subtract_unsigned', 45, 123)
)
.then((ret) => console.log(ret))
.catch((err) => console.error(
'Error: [%s] %s: %s',
err.name,
err.message,
err.errors()[0].description,
))``````
``0``
``````result = client.query(
q.call("subtract_unsigned", 45, 123)
)
print(result)``````
``0``
``````result, err := client.Query(
f.Call("subtract_unsigned", 45, 123))

if err != nil {
fmt.Fprintln(os.Stderr, err)
} else {
fmt.Println(result)
}``````
``0``
``````try
{
Value result = await client.Query(
Call("subtract_unsigned", 45, 123)
);
Console.WriteLine(result);
}
catch (Exception e)
{
Console.WriteLine(\$"ERROR: {e.Message}");
}``````
``LongV(0)``
``Call("subtract_unsigned", 45, 123)``
``0``
Query metrics:
•    bytesIn:  49

•   bytesOut:  14

• computeOps:   1

•   writeOps:   0