Math Functions

Math functions operate on Integer and Decimal values. When invoked on an empty collection, they return an empty collection. If the input is not a numeric type, they return an empty collection rather than raising an error.

abs

Returns the absolute value of the input number.

Signature:

abs() : Integer | Decimal

Return Type: Integer if the input is Integer, Decimal if the input is Decimal

Examples:

result, _ := fhirpath.Evaluate(resource, "(-5).abs()")
// 5 (Integer)

result, _ := fhirpath.Evaluate(resource, "(-3.14).abs()")
// 3.14 (Decimal)

result, _ := fhirpath.Evaluate(resource, "(42).abs()")
// 42 (positive values unchanged)

Edge Cases / Notes:

• Preserves the input type: Integer input returns Integer, Decimal input returns Decimal.
• Returns empty collection if the input is empty or not numeric.

ceiling

Returns the smallest integer greater than or equal to the input value.

Signature:

ceiling() : Integer

Return Type: Integer

Examples:

result, _ := fhirpath.Evaluate(resource, "(3.2).ceiling()")
// 4

result, _ := fhirpath.Evaluate(resource, "(-1.5).ceiling()")
// -1

result, _ := fhirpath.Evaluate(resource, "(5).ceiling()")
// 5 (integers are returned as-is)

Edge Cases / Notes:

• If the input is already an Integer, it is returned unchanged.
• Always rounds toward positive infinity.
• Returns empty collection if the input is empty or not numeric.

floor

Returns the largest integer less than or equal to the input value.

Signature:

floor() : Integer

Return Type: Integer

Examples:

result, _ := fhirpath.Evaluate(resource, "(3.8).floor()")
// 3

result, _ := fhirpath.Evaluate(resource, "(-1.2).floor()")
// -2

result, _ := fhirpath.Evaluate(resource, "(7).floor()")
// 7 (integers are returned as-is)

Edge Cases / Notes:

• If the input is already an Integer, it is returned unchanged.
• Always rounds toward negative infinity.
• Returns empty collection if the input is empty or not numeric.

truncate

Returns the integer portion of the input value, truncating toward zero.

Signature:

truncate() : Integer

Return Type: Integer

Examples:

result, _ := fhirpath.Evaluate(resource, "(3.9).truncate()")
// 3

result, _ := fhirpath.Evaluate(resource, "(-3.9).truncate()")
// -3

result, _ := fhirpath.Evaluate(resource, "(5).truncate()")
// 5 (integers are returned as-is)

Edge Cases / Notes:

• Unlike floor, truncate always rounds toward zero. For negative values, truncate(-3.9) returns -3 while floor(-3.9) returns -4.
• If the input is already an Integer, it is returned unchanged.
• Returns empty collection if the input is empty or not numeric.

round

Rounds the input value to the specified number of decimal places.

Signature:

round([precision : Integer]) : Decimal

Parameters:

Return Type: Decimal (or Integer if input is Integer)

Examples:

result, _ := fhirpath.Evaluate(resource, "(3.456).round(2)")
// 3.46

result, _ := fhirpath.Evaluate(resource, "(3.5).round()")
// 4 (default precision is 0)

result, _ := fhirpath.Evaluate(resource, "(2.345).round(1)")
// 2.3

Edge Cases / Notes:

• If no precision is specified, defaults to 0 (rounds to nearest integer).
• If the input is an Integer, it is returned unchanged.
• Uses banker’s rounding (round half to even) via the shopspring/decimal library.
• Returns empty collection if the input is empty or not numeric.

exp

Returns e raised to the power of the input value.

Signature:

exp() : Decimal

Return Type: Decimal

Examples:

result, _ := fhirpath.Evaluate(resource, "(0).exp()")
// 1.0 (e^0 = 1)

result, _ := fhirpath.Evaluate(resource, "(1).exp()")
// 2.718281828... (e^1 = e)

result, _ := fhirpath.Evaluate(resource, "(2).exp()")
// 7.389056099...

Edge Cases / Notes:

• Always returns a Decimal, even if the input is an Integer.
• Uses Go’s math.Exp function.
• Returns empty collection if the input is empty or not numeric.

ln

Returns the natural logarithm (base e) of the input value.

Signature:

ln() : Decimal

Return Type: Decimal

Examples:

result, _ := fhirpath.Evaluate(resource, "(1).ln()")
// 0.0 (ln(1) = 0)

result, _ := fhirpath.Evaluate(resource, "(2.718281828).ln()")
// ~1.0

result, _ := fhirpath.Evaluate(resource, "(10).ln()")
// 2.302585093...

Edge Cases / Notes:

• Returns empty collection if the input value is less than or equal to zero.
• Always returns a Decimal.
• Returns empty collection if the input is empty or not numeric.

log

Returns the logarithm of the input value with the specified base.

Signature:

log(base : Integer | Decimal) : Decimal

Parameters:

Return Type: Decimal

Examples:

result, _ := fhirpath.Evaluate(resource, "(100).log(10)")
// 2.0

result, _ := fhirpath.Evaluate(resource, "(8).log(2)")
// 3.0

result, _ := fhirpath.Evaluate(resource, "(27).log(3)")
// 3.0

Edge Cases / Notes:

• Returns empty collection if the input value is less than or equal to zero.
• Returns empty collection if the base is less than or equal to zero, or equals 1.
• Computed as ln(value) / ln(base).
• Returns empty collection if the input is empty or not numeric.

power

Returns the input value raised to the specified exponent.

Signature:

power(exponent : Integer | Decimal) : Integer | Decimal

Parameters:

Return Type: Decimal

Examples:

result, _ := fhirpath.Evaluate(resource, "(2).power(3)")
// 8.0

result, _ := fhirpath.Evaluate(resource, "(4).power(0.5)")
// 2.0 (square root)

result, _ := fhirpath.Evaluate(resource, "(10).power(0)")
// 1.0

Edge Cases / Notes:

• Always returns a Decimal value.
• Returns empty collection if the result is NaN or Inf (e.g., 0.power(-1)).
• Returns empty collection if the input is empty or not numeric.

sqrt

Returns the square root of the input value.

Signature:

sqrt() : Decimal

Return Type: Decimal

Examples:

result, _ := fhirpath.Evaluate(resource, "(16).sqrt()")
// 4.0

result, _ := fhirpath.Evaluate(resource, "(2).sqrt()")
// 1.4142135623...

result, _ := fhirpath.Evaluate(resource, "(0).sqrt()")
// 0.0

Edge Cases / Notes:

• Returns empty collection if the input value is negative.
• Always returns a Decimal.
• Equivalent to power(0.5).
• Returns empty collection if the input is empty or not numeric.