Is a

Evaluates to true if a value is of the specified type, false otherwise.Syntax:

<value> is a[n] {array | boolean | color | date | integer | number | point | rect | ASCII string }

Examples:

"1/16/98" is a date -- evaluates to true

1 is a boolean -- evaluates to false

45.4 is an integer -- evaluates to false

"red" is a color -- evaluates to true

local tArray
put "test" into tArray[1] 
put tArray is an array -- evaluates to true

numToChar(128) is an ASCII string -- evaluates to false

Use the is a operator to validate data to make sure it's the right type.

This operator is useful for checking whether the user has entered data correctly, and for checking parameters before sending them to a handler to avoid a script error caused by feeding data of one type to an operator or function that requires a different type.

A value is a(n):

• array(keyword) if its keys function is not empty.
• boolean or logical if it is one of the two constants true or false
• color if it is a valid color reference
• date if it is in one of the formats produced by the date or time

 functions 

• integer(keyword) if it consists of digits (with an optional leading

 minus sign), or an hexadecimal number (such as 0x0F9B)

• number if it consists of digits, optional leading minus sign, optional

 decimal point, and optional "E" or "e" (scientific notation), or an
 optional leading minus sign and infinity or inf

• point if it consists of two numbers separated by a comma
• rect if it consists of four numbers separated by commas
• ASCII string if it does not contain any characters greater than

 charToNum(127) 

All the types other than boolean can also include leading or trailing white space characters.

To ensure compatibility with SuperCard stacks, the is a color operator returns true for any integer, although integers are not valid colors in LiveCode. If you need to strictly verify a color then you can write a wrapper function to do so that checks that the color is not an integer.

The range of dates that LiveCode can handle is limited by the operating system's date routines. In particular, Windows systems are limited to dates after 1/1/1970. This means that the is a date operator will return false for dates before 1/1/1970 on Windows.

The is a operator is the logical inverse of the is not a operator. When one is true, the other is false.

Changes: The is an array(keyword) form was added in version 2.9

Parameters:

• value: Any source of value.

See also: isNumber (function),keys (function),time (function),is not a (operator),