SuperDB

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 often used to determine the existence of fields in a 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 messy data when applying conditional logic based on the presence of certain fields:

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

Examples

# spq
values {yes:has(foo),no:has(bar)}
# input
{foo:10}
# expected output
{yes:true,no:false}

# spq
values {yes: has(foo[1]),no:has(foo[4])}
# input
{foo:[1,2,3]}
# expected output
{yes:true,no:false}

# spq
values {yes:has(foo.bar),no:has(foo.baz)}
# input
{foo:{bar:"value"}}
# expected output
{yes:true,no:false}

# spq
values {yes:has(foo+1),no:has(bar+1)}
# input
{foo:10}
# expected output
{yes:true,no:false}

# spq
values has(bar)
# input
1
# expected output
false

# spq
values has(x)
# input
{x:error("missing")}
# expected output
false