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Extending functions
You can extend any previously-declared function using the .extend docs ↗ function within a scope. The extension wraps the original function, letting you transform, decorate, or replace its output without losing the original definition.
Example 1
.function {greet}
name:
Hello, .name!
.extend {greet}
super:
.super::uppercase
.greet {world}HELLO, WORLD!
Parameters
The wrapper body is a lambda. Its first explicit parameter, conventionally called super, is bound to the result of the original function. Any further parameters must match the names of the original function’s parameters and let you read the arguments the caller passed.
Example 2
The output may depend on an argument’s value:
.function {greet}
name:
Hello, .name!
.extend {greet}
super name:
.if {.name::equals {world}}
.super::uppercase
.ifnot {.name::equals {world}}
.super
.greet {world}
.greet {John}HELLO, WORLD!
Hello, John!
All wrapper parameters are always optional. You only need to declare the parameters you actually use in the body.
Example 3
Built-in functions can be extended:
.extend {heading}
super depth:
.let {.depth::islower than:{4}}
.if {.1}
.container background:{teal} fullwidth:{yes}
.super
.ifnot {.1}
.super
.heading {H2} depth:{2} indexed:{no}
.heading {H3} depth:{3} indexed:{no}
.heading {H4} depth:{4} indexed:{no}