is_map

From the SETL Wiki

is_map
Category	predicate
Syntax	prefix
Compatibility
CIMS SETL	yes
SETL-S	yes
SETL2	yes
GNU SETL	yes

Contents 1 Purpose 2 Synopsis 3 Description 4 Examples

Purpose

Determine whether the specified value is a map

Synopsis

 is_map x

Description

Returns true if:

1. x is a set and
2. every element of x is a pair, i.e. a tuple of length 2 whose first element is not om.

SETL2 also allows a tuple of length 1 in a map, representing a key that is mapped to om.

Examples

1. is_map {['a', 1], ['b', 2]}
   

   Result: true

2. is_map {}
   

   Result: true

3. is_map {42}
   

   Result: false

4. is_map {['a', 1], 42}
   

   Result: false

5. is_map {['a', 1], [om, 2]}
   

   Result: false

6. is_map({['a', 1], ['b']})
   

   Result: true in SETL2, false in all other implementations. Note that SETL2 requires the parentheses around the operand.