Build a list of Colour values and check if a specific colour is in the palette.

← Operators and Expressions · Ref: Q1207

EK9 Colour uses hex literals (#RRGGBB). Store colours in a List and use the 'contains' operator for membership testing.

PALETTE

  palette <- [#FF0000, #00FF00, #0000FF]

MEMBERSHIP CHECK

  if palette contains targetColour
    stdout.println("Colour found in palette")

The 'contains' operator checks element membership in a List. It uses the == operator internally, so it works with any type that supports equality. Colour literals and the == operator make palette management simple and type-safe.

See Q1159 for list contains. See Q1190 for colour equality. See Q1101 for is in with lists.

Example

defines module qa.operators.colourpalette

  defines program

    ColourPaletteDemo()
      stdout <- Stdout()

      // === BUILD PALETTE ===

      red <- #FF0000
      green <- #00FF00
      blue <- #0000FF
      palette <- [red, green, blue]

      // === MEMBERSHIP CHECK ===

      targetColour <- #FF0000
      if palette contains targetColour
        stdout.println(`${targetColour} is in the palette`)

      // === COLOUR NOT IN PALETTE ===

      yellow <- #FFFF00
      if not (palette contains yellow)
        stdout.println(`${yellow} is not in the palette`)

      // === CHECK MULTIPLE COLOURS ===

      candidates <- [#FF0000, #FFFF00, #0000FF, #FF00FF]
      for candidate in candidates
        if palette contains candidate
          stdout.println(`${candidate}: in palette`)
        else
          stdout.println(`${candidate}: not in palette`)

      // === ADD TO PALETTE AND RECHECK ===

      extendedPalette <- palette + yellow
      if extendedPalette contains yellow
        stdout.println(`Yellow added to extended palette`)

      // === STREAM OUTPUT ===

      stdout.println("Full palette:")
      cat palette > stdout

Other ways to ask this

Create a palette of colours and test membership using the contains operator.
I need to verify whether a given colour exists in a predefined set.
In CSS I'd compare hex codes as strings. How does EK9 check colour membership in a list?
Given a list of Colour literals, check if a target colour is present.

Coming from another language?

Java: list.contains(color) with java.awt.Color. Python: color in palette with tuples or custom class. JavaScript: array.includes(color) with string hex codes. CSS: string comparison. EK9: palette contains targetColour — operator syntax, typed Colour values, no string comparison needed.

Keywords: palette, collection, rgb, colour, check, membership, hex, contains, list, literal