QGIS/resources/function_help/json/op_minus

{
  "name": "-",
  "type": "operator",
  "groups": ["Operators"],
  "description": "Subtraction of two values. If one of the values is NULL the result will be NULL.",
  "arguments": [
        { "arg": "a", "description": "value" },
        { "arg": "b", "description": "value" }
  ],
  "examples": [
	{ "expression":"5 - 4", "returns":"1"},
	{ "expression":"5 - NULL", "returns":"NULL"},
	{ "expression":"to_datetime('2012-05-05 12:00:00') - to_interval('1 day 2 hours')", "returns":"2012-05-04T10:00:00"}
  ]
}