Selecting runs

select (Python, MATLAB, Julia), gamut_select (C) and --where (the command line) take a condition and return the positions of the rows that meet it, in increasing order. The language is the same everywhere, because the core evaluates it.

mach > 0.7
status == converged
model == "k-omega SST" or alpha <= 0
(mach>0.4)and(alpha<5)
speed >= 20 and not (gamma > 1)

Comparisons

A comparison is a name, an operator and a value.

Name	Operators	Value
a parameter or a scalar	== != < <= > >=	a decimal number: 0.7, -2, 1e-5
a label	== !=	one of the label's names, in double quotes if it has spaces or any of ( ) = ! < >

Operators and parentheses need no spaces around them. A single = is not an operator; the message says which ones are. A name that itself holds a double quote cannot be written in a condition; choose those runs by position instead.

Combining

not binds tightest, then and, then or; parentheses group. a or b and c is a or (b and c).

Missing values

A result that is missing (NaN) meets no comparison, != included, so a failed run's cl is neither <= 0.5 nor > 0.5. not turns that into a match: not (cl > 0.5) keeps the failed runs, while cl <= 0.5 leaves them out.

Refusals

A condition that does not parse, a name the file does not have, a label compared with <, or a label value that is not in its table is refused with a message saying what and where (the character position for a syntax error), and nothing is returned.

Limits

A selection reads the columns it compares a block of rows at a time, so memory stays bounded. Files with more than 2²⁷ rows (about 134 million) are refused; select on a subset extracted first.