Valtype

Valtype is Goblin's type introspection keyword. It tells you what type a value is at runtime. vt is the shorthand version.

Sometimes you need to know what type a value actually is — when you're debugging, when you're working with data you didn't create, or when a variable could hold different types depending on what happened before. valtype answers that question.

It is available in four equivalent forms:

age.vt
age.valtype
vt(age)
valtype(age)

age.vt
age.valtype
vt(age)
valtype(age)

All four do the same thing. Use whichever reads most naturally in context.

vt works on any expression — not just named variables:

(1 + 2).vt      /// -> "int"
"hello".vt      /// -> "str"

(1 + 2).vt      /// -> "int"
"hello".vt      /// -> "str"

Basic Usage

name   | "Daniel"
age    | 46
active | true
score  | 99.5

name.vt     /// -> "str"
age.vt      /// -> "int"
active.vt   /// -> "bool"
score.vt    /// -> "float"

name   | "Daniel"
age    | 46
active | true
score  | 99.5

name.vt     /// -> "str"
age.vt      /// -> "int"
active.vt   /// -> "bool"
score.vt    /// -> "float"

Inferred vs. Type-Locked Variables

What vt reports depends on how the variable was declared.

An unlocked variable reports its current runtime type:

age | 46
age.vt      /// -> "int"

age |= 99.5
age.vt      /// -> "float"

age | 46
age.vt      /// -> "int"

age |= 99.5
age.vt      /// -> "float"

A type-locked variable always reports its declared lock type, regardless of the stored value:

age.i32 | 46
age.vt      /// -> "i32"

age.i32 | 46
age.vt      /// -> "i32"

A type-locked collection reports the lock type qualified by the collection kind:

zip_codes.int | [90210, 80924]
zip_codes.vt  /// -> "array(int)"

scores.float | { alice: 9.8, bob: 8.5 }
scores.vt    /// -> "map(float)"

zip_codes.int | [90210, 80924]
zip_codes.vt  /// -> "array(int)"

scores.float | { alice: 9.8, bob: 8.5 }
scores.vt    /// -> "map(float)"

Comparing Types

vt returns a string, so you can compare it directly:

age | 46

if age.vt == "int"
    say "it's an integer"
xx

age | 46

if age.vt == "int"
    say "it's an integer"
xx

On Objects, Classes, and Enums

vt works on variables, object instances, and class definitions themselves.

On an object instance, vt returns "object":

rome <> Kingdom | name: "Rome", gold: 1000
rome.vt     /// -> "object"

rome <> Kingdom | name: "Rome", gold: 1000
rome.vt     /// -> "object"

On a class definition, vt returns "class":

Kingdom.vt  /// -> "class"

Kingdom.vt  /// -> "class"

On an enum value, vt returns "enum":

status | Status::idle
status.vt   /// -> "enum"

status | Status::idle
status.vt   /// -> "enum"