divide, ln, log, mod: Clarified behavior for 0 input / infinity results

CHANGELOG.md

@@ -12,6 +12,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- `divide`: Clarified behavior for division by 0
+- `ln` and `log`: Clarified that for x = 0 -infinity is returned
+- `mod`: Clarified behavior for y = 0
 - `filter_bbox`, `load_collection`, `load_stac`: Clarified that the bounding box is reprojected to the CRS of the spatial data cube dimensions if required.
 - `filter_spatial`: Clarified that masking is applied using the given geometries. [#469](https://github.com/Open-EO/openeo-processes/issues/469)
 - `sqrt`: Clarified that NaN is returned for negative numbers.

divide.json

@@ -1,7 +1,7 @@
 {
     "id": "divide",
     "summary": "Division of two numbers",
-    "description": "Divides argument `x` by the argument `y` (*`x / y`*) and returns the computed result.\n\nNo-data values are taken into account so that `null` is returned if any element is such a value.\n\nThe computations follow [IEEE Standard 754](https://ieeexplore.ieee.org/document/8766229) whenever the processing environment supports it. Therefore, a division by zero results in ±infinity if the processing environment supports it. Otherwise, a `DivisionByZero` exception must the thrown.",
+    "description": "Divides argument `x` by the argument `y` (*`x / y`*) and returns the computed result.\n\nNo-data values are taken into account so that `null` is returned if any element is such a value.\n\nThe computations follow [IEEE Standard 754](https://ieeexplore.ieee.org/document/8766229) whenever the processing environment supports it. A division by zero results in:\n\n- +infinity for `x` > 0,\n- -infinity for `x` < 0,\n- `NaN` for `x` = 0,\n- or otherwise, throws a `DivisionByZero` exception if the other options are not supported by the processing environment.",
     "categories": [
         "math"
     ],
@@ -76,4 +76,4 @@
             "title": "IEEE Standard 754-2019 for Floating-Point Arithmetic"
         }
     ]
-}
+}

ln.json

@@ -1,7 +1,7 @@
 {
     "id": "ln",
     "summary": "Natural logarithm",
-    "description": "The natural logarithm is the logarithm to the base *e* of the number `x`, which equals to using the *log* process with the base set to *e*. The natural logarithm is the inverse function of taking *e* to the power x.\n\nThe no-data value `null` is passed through.\n\nThe computations follow [IEEE Standard 754](https://ieeexplore.ieee.org/document/8766229) whenever the processing environment supports it. Therefore, *`ln(0)`* results in ±infinity if the processing environment supports it or otherwise an exception is thrown.",
+    "description": "The natural logarithm is the logarithm to the base *e* of the number `x`, which equals to using the *log* process with the base set to *e*. The natural logarithm is the inverse function of taking *e* to the power x.\n\nThe no-data value `null` is passed through.\n\nThe computations follow [IEEE Standard 754](https://ieeexplore.ieee.org/document/8766229) whenever the processing environment supports it. Therefore, *`ln(0)`* results in -infinity if the processing environment supports it. Otherwise, an exception is thrown.",
     "categories": [
         "math > exponential & logarithmic"
     ],
@@ -64,4 +64,4 @@
             "result": true
         }
     }
-}
+}

log.json

@@ -1,7 +1,7 @@
 {
     "id": "log",
     "summary": "Logarithm to a base",
-    "description": "Logarithm to the base `base` of the number `x` is defined to be the inverse function of taking b to the power of x.\n\nThe no-data value `null` is passed through and therefore gets propagated if any of the arguments is `null`.\n\nThe computations follow [IEEE Standard 754](https://ieeexplore.ieee.org/document/8766229) whenever the processing environment supports it. Therefore, `log(0, 2)` results in ±infinity if the processing environment supports it or otherwise an exception is thrown.",
+    "description": "Logarithm to the base `base` of the number `x` is defined to be the inverse function of taking b to the power of x.\n\nThe no-data value `null` is passed through and therefore gets propagated if any of the arguments is `null`.\n\nThe computations follow [IEEE Standard 754](https://ieeexplore.ieee.org/document/8766229) whenever the processing environment supports it. Therefore, having `x` set to `0` with any base results in -infinity if the processing environment supports it. Otherwise, an exception is thrown.",
     "categories": [
         "math > exponential & logarithmic"
     ],
@@ -78,4 +78,4 @@
             "title": "IEEE Standard 754-2019 for Floating-Point Arithmetic"
         }
     ]
-}
+}

mod.json

@@ -1,7 +1,7 @@
 {
     "id": "mod",
     "summary": "Modulo",
-    "description": "Remainder after a division of `x` by `y` for both integers and floating-point numbers.\n\nThe result of a modulo operation has the sign of the divisor. The handling regarding the sign of the result [differs between programming languages](https://en.wikipedia.org/wiki/Modulo_operation#In_programming_languages) and needs careful consideration to avoid unexpected results.\n\nThe no-data value `null` is passed through and therefore gets propagated if any of the arguments is `null`. A modulo by zero results in ±infinity if the processing environment supports it. Otherwise, a `DivisionByZero` exception must the thrown.",
+    "description": "Remainder after a division of `x` by `y` for both integers and floating-point numbers.\n\nThe result of a modulo operation has the sign of the divisor. The handling regarding the sign of the result [differs between programming languages](https://en.wikipedia.org/wiki/Modulo_operation#In_programming_languages) and needs careful consideration to avoid unexpected results.\n\nThe no-data value `null` is passed through and therefore gets propagated if any of the arguments is `null`. If `y` is set to 0 this results in:\n\n- +infinity for `x` > 0,\n- -infinity for `x` < 0,\n- `NaN` for `x` = 0,\n- or otherwise, throws a `DivisionByZero` exception if the other options are not supported by the processing environment.",
     "categories": [
         "math"
     ],
@@ -92,4 +92,4 @@
             "title": "Modulo explained by Wikipedia"
         }
     ]
-}
+}