rswipl (version 9.3.21)

query: Create a query

Description

Create a query

Usage

query(
  q = call("member", expression(X), list(quote(a), "b", 3L, 4, TRUE, expression(Y)))
)

Value

If the creation of the query succeeds, TRUE

Arguments

q

an R call. The R call consists of symbols, integers and real numbers, character strings, boolean values, expressions, lists, and other calls. Vectors of booleans, integers, floating point numbers, and strings with length N > 1 are translated to prolog compounds !/N, %/N, #/N and $$/N, respectively.

Details

SWI-Prolog does not allow multiple open queries. If another query is open, it it is closed and a warning is shown.

See Also

submit() for submitting a query

clear() to close the currently open query

Examples

query(call("writeln", function(x) {sin(x)}))
submit()
clear()

query(call("=", expression(X), function(x) {sin(x)}))
submit()
clear()

query(call("member", expression(X), list(quote(a), "b", 3L, 4, TRUE, expression(Y),
  NA, NaN, Inf, NULL, NULL, function(x) {y <- sin(x); y^2}, NULL)))
submit() # X = a
submit() # X = "b"
submit() # X = 3L
submit() # X = 4.0
submit() # X = TRUE
submit() # X = expression(Y) or Y = expression(X)
submit() # X = NA
submit() # X = NaN
submit() # X = Inf
submit() # X = NULL
submit() # X = NULL
submit() # X = function(x) {y <- sin(x); y^2}))
submit() # X = NULL
submit() # FALSE (no more results)
submit() # warning that no query is open

query(call("member", expression(X), list(quote(a), "b", 3L, 4)))
query(call("member", expression(X), list(TRUE, expression(Y)))) # warning that another query is open
clear()