Applying logical and to list of boolean values

scala boolean logical-operators fold
user3277752 picture user3277752 · Mar 19, 2014 · Viewed 20k times · Source

Consider the following list of Boolean values in Scala

List(true, false, false, true)

How would you using either foldRight or foldLeft emulate the function of performing a logical AND on all of the values within the list?

Answer

drexin picture drexin · Mar 19, 2014

Instead of using foldLeft/Right, you can also use forall(identity) for the logical AND, or exists(identity) for the logical OR.

edit: The benefit of these functions is the early exit. If forall hits a false or exists a true, they will immediately return.

Related questions

How to use java.String.format in Scala?

I am trying to use a .format method of a string. But if I place %1, %2, etc. in the string, java.util.UnknownFormatConversionException is thrown pointing to a confusing Java source code piece: private void checkText(String s) { int idx; // If …

Read More
How can I change column types in Spark SQL's DataFrame?

Suppose I'm doing something like: val df = sqlContext.load("com.databricks.spark.csv", Map("path" -> "cars.csv", "header" -> "true")) df.printSchema() root |-- year: string (nullable = true) |-- make: string (nullable = true) |-- model: string (nullable = …

Read More
Spark - load CSV file as DataFrame?

I would like to read a CSV in spark and convert it as DataFrame and store it in HDFS with df.registerTempTable("table_name") I have tried: scala> val df = sqlContext.load("hdfs:///csv/file/dir/file.csv") Error …

Read More