kex docs Standard Library 0.4.0-alpha kex.run ↗

Truthyableprelude

trait Truthyable

Truthyable: what counts as true when a value is used as a condition.

The rule is Crystal's, and it is short: only false, None and () are falsy. Everything else is truthy, including 0, "" and [], which some languages treat as false and Kex deliberately does not.

0.truthy?       # => true
"".truthy?      # => true
[].truthy?      # => true
None.truthy?    # => false
false.truthy?   # => false

When you want the "is there anything here" question instead, that is Blankable's blank? / present?.

There is no NaN to consider: a float operation that would produce one raises instead, matching BEAM (see nonFiniteFloatError in src/interpreter/value.cxx).

truthy?

Returns true when the value counts as true in a condition.

truthy? : Bool

Returns: Bool — true unless the value is false, None or ()

Examples
1.truthy?        # => true
None.truthy?     # => false

make Bool implements Truthyable

make Integer implements Truthyable

truthy?

Always true, including for zero.

Zero is a number, not an absence. Compare it explicitly when zero means something: count == 0.

truthy? : Bool

Returns: Bool — always true

Examples
0.truthy?    # => true
42.truthy?   # => true

make Float implements Truthyable

truthy?

Always true, including for zero.

truthy? : Bool

Returns: Bool — always true

Examples
0.0.truthy?   # => true

make String implements Truthyable

truthy?

Always true, including for the empty string.

Use blank? from Blankable when an empty or whitespace-only string should count as nothing.

truthy? : Bool

Returns: Bool — always true

Examples
"".truthy?      # => true
"".blank?       # => true   (the question usually meant)

make Optional<X> implements Truthyable

truthy?

Returns true for a Just and false for None.

The one type where truthiness is genuinely about presence, which is what makes an optional usable directly as a condition.

truthy? : Bool

Returns: Bool — true when a value is present

Examples
Just(0).truthy?    # => true
None.truthy?       # => false

make [X] implements Truthyable

truthy?

Always true, including for the empty list.

Use empty? or blank? when an empty list should count as nothing.

truthy? : Bool

Returns: Bool — always true

Examples
[].truthy?   # => true
[].blank?    # => true   (the question usually meant)

make Map<K, V> implements Truthyable

truthy?

Always true, including for the empty map.

truthy? : Bool

Returns: Bool — always true

Examples
{}.truthy?   # => true
{}.blank?    # => true   (the question usually meant)