Merge pull request #9 from Virnkord/math

5.7 Math functions ln() and log()

CHANGELOG.md

@@ -3,6 +3,10 @@
 This log documents significant changes for each release.  This project follows
 [Semantic Versioning](http://semver.org/).
 
+## [0.13.0] - 2019-05-21
+### Added
+- Functions ln() and log() in 5.7 (Math) of the FHIRPath specification.
+
 ## [0.12.2] - 2019-05-15
 ### Fixed
 - Corrected output in the demo website for results containing dates and times.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "fhirpath",
-  "version": "0.12.2",
+  "version": "0.13.0",
   "description": "A FHIRPath engine",
   "main": "src/fhirpath.js",
   "dependencies": {

src/fhirpath.js

@@ -96,6 +96,9 @@ engine.invocationTable = {
   replaceMatches: {fn: strings.replaceMatches,   arity: {2: ["String", "String"]}},
   length:         {fn: strings.length },
 
+  ln:             {fn: math.ln},
+  log:            {fn: math.log, arity:  {1: ["Number"]}, nullable: true},
+
   now:            {fn: datetime.now },
   today:          {fn: datetime.today },
 

src/math.js

@@ -6,6 +6,25 @@
 
 var engine = {};
 
+function ensureNumberSingleton(x){
+  if (typeof x != 'number'){
+    if (x.length == 1){
+      return x[0];
+    }else{
+      throw new Error("Expected number, but got " + JSON.stringify(x));
+    }
+  }else{
+    return x;
+  }
+}
+
+function isEmpty(x) {
+  if(typeof(x) == 'number'){
+    return false;
+  }
+  return x.length == 0;
+}
+
 engine.amp = function(x, y){
   return (x || "") + (y || "");
 };
@@ -46,5 +65,23 @@ engine.mod = function(x, y){
   return x % y;
 };
 
+engine.ln = function(x){
+  if (isEmpty(x)){
+    return [];
+  }else{
+    let num = ensureNumberSingleton(x);
+    return Math.log(num);
+  }
+};
+
+engine.log = function(x, base){
+  if (isEmpty(x) || isEmpty(base)){
+    return [];
+  }else{
+    let num = ensureNumberSingleton(x);
+    let num2 = ensureNumberSingleton(base);
+    return (Math.log(num) / Math.log(num2));
+  }
+};
 
 module.exports = engine;

test/cases/5.7_math.yaml

@@ -0,0 +1,41 @@
+tests:
+  - desc: '5.7 Math'
+  - desc: '5.7.5 ln() : Decimal'
+  - desc: '** Can take the natural logarithm of the number'
+    expression: Math.n1.ln()
+    result: [0]
+  - desc: '** Empty result when taking logarithm from empty collection'
+    expression: Math.n2.ln()
+    result: []
+  - desc: '** Error taking logarithm due to too many input parameters'
+    expression: Math.n3.ln(n4)
+    error: true
+  - desc: '** Error taking logarithm if the input collection contains multiple items'
+    expression: Math.arr.ln()
+    error: true
+
+  - desc: '5.7.6  log(base : Decimal) : Decimal'
+  - desc: '** Can take the logarithm of the number with a given base'
+    expression: Math.n4.log(2)
+    result: [3]
+  - desc: '** Empty result when taking logarithm from empty collection'
+    expression: Math.n2.log(8)
+    result: []
+  - desc: '** Empty result when taking logarithm with empty base'
+    expression: Math.n3.log(n2)
+    result: []
+  - desc: '** Error taking logarithm if the input collection contains multiple items'
+    expression: Math.arr.log(8)
+    error: true
+  - desc: '** Error taking logarithm due to too many input parameters'
+    expression: Math.n3.log([3, 5])
+    error: true
+
+subject:
+  resourceType: Math
+  n1: 1
+  n2: []
+  n3: 2
+  n4: 8
+  arr: [3, 5]
+  t: true