Count matching integer values

Write the ordinary calculation you need. For a simple comparison over an i32 or u32 column, the default optimized profile can count matches with SIMD: the CPU compares four values together. You do not choose a vector width or handle leftover rows.

class Sample:
    score: i32

def main() -> Result[(), AppendError[Sample] | IoError]:
    mut samples = clist[Sample]()
    for score in range(9):
        samples.append(Sample(i32(score)))?
    matches = samples.column(Sample.score).filter(def(x: &i32) -> bool: *x > 5i32).count()
    print(matches)?
    Ok(())

3

Use runtime bounds

Bounds do not need to be constants. Capture their scalar values to count a range:

class Sample:
    score: i32

def count_between(samples: &clist[Sample], low: i32, high: i32) -> i64:
    samples.column(Sample.score).filter(def [low, high](x: &i32) -> bool: *x >= low and *x < high).count()

def main() -> Result[(), AppendError[Sample] | IoError]:
    mut samples = clist[Sample]()
    for score in range(9):
        samples.append(Sample(i32(score)))?
    print(count_between(&samples, 2i32, 7i32))?
    Ok(())

5

[low, high] captures copies of the bounds. They can come from function arguments or parsed input. The closure keeps those values even if an original binding later changes. Write two comparisons with and; Plenty does not use chained comparison syntax.

This is the same program in normal and optimized builds. The SIMD path recognizes one comparison, or two comparisons joined by and, against constants or up to two immutable scalar captures of the column’s type. Borrowed captures, arithmetic inside the predicate, or, and extra adapters keep scalar execution. Other calculations, including the floating-point average in the previous lesson, keep ordinary scalar execution. All scans still run on one thread. See the columnar-list reference for the precise optimization limits, allocation, borrowing and representation.