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MEANS

MEANS gives the body of a function or a value, written without DECIDE.

Syntax

name MEANS expression
name input1 input2 ... MEANS expression

name MEANS expression defines the same thing as DECIDE name IS expression. The two keywords do not mix: DECIDE name MEANS ... and a top-level name IS ... are syntax errors.

Example file:

-- MEANS keyword examples

-- Basic MEANS Usage

-- Simple value definition
greeting MEANS "Hello, World!"
answer MEANS 42

#EVAL greeting
#EVAL answer

-- Functions with MEANS

GIVEN x IS A NUMBER
double x MEANS x TIMES 2

GIVEN a IS A NUMBER, b IS A NUMBER
add a b MEANS a PLUS b

#EVAL double 21
#EVAL add 10 32

-- Multi-line Function Bodies

GIVEN n IS A NUMBER
GIVETH A NUMBER
factorial n MEANS
  IF n EQUALS 0
  THEN 1
  ELSE n TIMES factorial (n MINUS 1)

#EVAL factorial 6

-- MEANS with WHERE Clauses

GIVEN radius IS A NUMBER
circumference radius MEANS
  2 TIMES pi TIMES radius
  WHERE
    pi MEANS 3.14159

#EVAL circumference 10

-- Nested WHERE
outerFunction MEANS
  innerResult TIMES 2
  WHERE
    innerResult MEANS
      baseValue PLUS 10
      WHERE
        baseValue MEANS 5

#EVAL outerFunction

-- MEANS vs IS Comparison

-- Using MEANS for definitions
valueWithMeans MEANS 100
valueWithMeans2 MEANS 200

#EVAL valueWithMeans
#EVAL valueWithMeans2

-- MEANS in Complex Expressions

GIVEN items IS A LIST OF NUMBER
sumItems items MEANS
  CONSIDER items
  WHEN EMPTY THEN 0
  WHEN head FOLLOWED BY tail THEN head PLUS sumItems tail

#EVAL sumItems (LIST 1, 2, 3, 4, 5)

Examples

`the greeting` MEANS "Hello, World!"

GIVEN n IS A NUMBER
GIVETH A NUMBER
`factorial of` n MEANS
  IF n EQUALS 0
  THEN 1
  ELSE n TIMES `factorial of` (n MINUS 1)

The inputs can sit before, between or after the words of the name, so a call reads like a sentence:

GIVEN buyer IS A STRING
      seller IS A STRING
GIVETH A STRING
buyer `buys from` seller MEANS CONCAT buyer, " buys from ", seller

#EVAL "Alice" `buys from` "Bob"

See Mixfix functions.

Other places MEANS appears

  • Under WHERE, each local definition uses MEANS; see LET and WHERE.
  • After LET, MEANS is one of the keywords that can introduce a definition, with IS, BE, MEAN and =.
  • Inside a DECLARE … HAS, a field with MEANS is a computed field; see DECLARE: Computed fields.
  • A function can be written as several MEANS lines, one per case; see DECIDE: Several clauses.