Fhirpath

Patient.name.given              // Navigate to given names
Patient.name[0].given           // First name's given (0-based indexing)
Patient.name.first().given      // Equivalent using first()
Observation.value.ofType(Quantity).unit  // Filter by type then navigate

name.exists()                           // true if any names
name.exists(use = 'official')           // true if any official names
name.all(given.exists())                // true if all names have given
telecom.where(system='phone').empty()   // true if no phone telecoms
name.count()                            // number of names

name.where(use = 'official')                    // Filter by criteria
entry.select(resource as Patient)               // Project/transform
name.select(given.first() + ' ' + family)       // Combine fields
telecom.distinct()                              // Remove duplicates
item.repeat(item)                               // Recursive traversal (unique)
expansion.repeat(contains)                      // Navigate tree structures

name[0]           // First item (0-based)
name.first()      // First item
name.last()       // Last item
name.tail()       // All but first
name.skip(2)      // Skip first 2
name.take(3)      // Take first 3
name.single()     // Error if not exactly one

name.given | name.family     // Union (removes duplicates)
a.union(b)                   // Same as |
a.combine(b)                 // Merge without removing duplicates
a.intersect(b)               // Items in both
a.exclude(b)                 // Items in a but not b

value is Quantity                    // Type check (returns Boolean)
value as Quantity                    // Cast (empty if wrong type)
entry.resource.ofType(Patient)       // Filter collection by type

'hello'.length()                     // 5
'hello'.substring(1, 3)              // 'ell'
'hello'.startsWith('he')             // true
'hello'.endsWith('lo')               // true
'hello'.contains('ell')              // true (different from contains operator)
'hello'.indexOf('l')                 // 2
'HELLO'.lower()                      // 'hello'
'hello'.upper()                      // 'HELLO'
'a-b-c'.replace('-', '_')            // 'a_b_c'
'abc'.matches('[a-z]+')              // true (partial match)
'abc'.matchesFull('[a-z]+')          // true (full match)
'a,b,c'.split(',')                   // {'a', 'b', 'c'}
('a' | 'b' | 'c').join(',')          // 'a,b,c'
'  hello  '.trim()                   // 'hello'

(-5).abs()              // 5
1.5.ceiling()           // 2
1.5.floor()             // 1
1.5.round()             // 2
1.5.truncate()          // 1
2.power(3)              // 8.0
9.sqrt()                // 3.0
2.718.ln()              // ~1.0
100.log(10)             // 2.0
0.exp()                 // 1.0

'42'.toInteger()              // 42
42.toString()                 // '42'
'3.14'.toDecimal()            // 3.14
'true'.toBoolean()            // true (also 't', 'yes', 'y', '1')
'2024-01-15'.toDate()         // @2024-01-15
'10:30:00'.toTime()           // @T10:30:00
'5 mg'.toQuantity()           // 5 'mg'
value.convertsToInteger()     // true if conversion would succeed

@2024-03-15.yearOf()                          // 2024
@2024-03-15.monthOf()                         // 3
@2024-03-15.dayOf()                           // 15
@2024-03-15T10:30:45.123.hourOf()             // 10
@2024-03-15T10:30:45.123.minuteOf()           // 30
@2024-03-15T10:30:45.123.secondOf()           // 45
@2024-03-15T10:30:45.123.millisecondOf()      // 123
@2024-03-15T10:30:00+10:00.timezoneOffsetOf() // 10.0
@2024-03-15T10:30:00.dateOf()                 // @2024-03-15
@2024-03-15T10:30:00.timeOf()                 // @T10:30:00

now()                                 // Current DateTime
today()                               // Current Date
timeOfDay()                           // Current Time
iif(condition, true-result, else)     // Conditional (short-circuit)
coalesce(a, b, c)                     // First non-empty (STU)
trace('label', projection)            // Debug logging
defineVariable('name', expr)          // Define variable for later use (STU)

(1 | 2 | 3).sum()                     // 6
(1 | 2 | 3).min()                     // 1
(1 | 2 | 3).max()                     // 3
(1 | 2 | 3).avg()                     // 2.0
values.aggregate($this + $total, 0)   // Custom aggregation

a = b       // Equal (empty if either empty)
a ~ b       // Equivalent (false if precisions differ, case-insensitive for strings)
a != b      // Not equal
a !~ b      // Not equivalent

a > b       // Greater than
a < b       // Less than
a >= b      // Greater or equal
a <= b      // Less or equal

a and b     // Three-valued AND
a or b      // Three-valued OR
a xor b     // Exclusive OR
a implies b // Implication
not()       // Negation (function, not operator)

5 + 3       // Addition (also string concatenation)
5 - 3       // Subtraction
5 * 3       // Multiplication
5 / 3       // Division (always Decimal)
5 div 3     // Integer division
5 mod 3     // Modulo
'a' & 'b'   // String concat (empty → empty string)

item in collection       // Membership
collection contains item // Containership (converse of in)
a | b                    // Union