has.md

Function

  has — test existence of values

Synopsis

has(val: any [, ... val: any]) -> bool

Description

The has function returns false if any of its arguments are error("missing") and otherwise returns true. has(e) is a shortcut for !missing(e).

This function is most often used to test the existence of certain fields in an expected record, e.g., has(a,b) is true when this is a record and has the fields a and b, provided their values are not error("missing").

It's also useful in shaping when applying conditional logic based on the presence of certain fields:

switch (
  case has(a) => ...
  case has(b) => ...
  default => ...
)

Examples

echo '{foo:10}' | super -z -c 'yield {yes:has(foo),no:has(bar)}' -
echo '{foo:[1,2,3]}' | super -z -c 'yield {yes: has(foo[0]),no:has(foo[3])}' -
echo '{foo:{bar:"value"}}' |
  super -z -c 'yield {yes:has(foo.bar),no:has(foo.baz)}' -
echo '{foo:10}' | super -z -c 'yield {yes:has(foo+1),no:has(bar+1)}' -
echo 1 | super -z -c 'yield has(bar)' -
echo '{x:error("missing")}' | super -z -c 'yield has(x)' -

=>

{yes:true,no:false}
{yes:true,no:false}
{yes:true,no:false}
{yes:true,no:false}
false
false