Entity

Entity – a single computable element in PapajScript.

History

The first entities, Number and String, were introduced on April 26, 2018 with the release of the RPN 0.4.0.

Entity types

Current usable entity types:

• Number, e.g. 5, 2, -10, 20.5 etc.
  More explanation here.
• String, e.g. "Hello world!", "Shalom!", "h" etc.
  More explanation here.
  See the functions for strings in the String package.
• Boolean, e.g. TRUE, FALSE
  See the logical functions here.
• Null, e.g. NULL
• Function, e.g. fun{ -1 * } etc.
  More explanation here.
• Exception, e.g. EXC (as of now just basic ones, to be improved)
• Array, e.g. [], [ 2 1 3 7 ], [ 10 times rand ]
  More explanation here.
  See the functions for arrays in the Array package.
• LogicalExpression, e.g. ( x 0 > )
  More explanation here.
• DateTime, e.g. "2005-04-02 21:37:00" Date.toDateTime More explanation here.
  See the functions for arrays in the Date package.

Quasi-types:

• InstructionBlock, e.g. { x 2 ^ 2 / }

Planned for the future

• Object
• File
• Dataframe

Current unusable data types:

• Unknown

Removed/replaced types:

• Expression, e.g. ( x 0 > ) – replaced by LogicalExpression in September 2020

Type casting

Syntax: X command

Programme Operand	Purpose
toString	convert to a string
toNumber	convert to a number
toBoolean	convert to a logical value true or false
toArray	build an array from N elements of the stack
toException	build an exception (if X is a string, then it creates an unraised exception with this string message)
Date.toDateTime	builds a datetime either from a string or a real number (assuming it represents Unix epoch time)
raiseException	same as above, but it raises exception too

Type checking

Syntax: X command

• type returns a string containing entity type, e.g. "String"
• isNumber, isBoolean, isString, isArray, isNull, isException, isLogicalExpression, isFunction, isDateTime – return TRUE or FALSE relatively if an entity is of a type mentioned in the function