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## org.apache.poi.ss.formula.eval
Class OperandResolver

    java.lang.Object
      org.apache.poi.ss.formula.eval.OperandResolver

    public final class OperandResolver

extends java.lang.Object

Provides functionality for evaluating arguments to functions and operators.

Author:
  Josh Micich, Brendan Nolan

Method Summary
`static ValueEval` | `chooseSingleElementFromArea(AreaEval ae, int srcCellRow, int srcCellCol)` Implements (some perhaps not well known) Excel functionality to select a single cell from an area depending on the coordinates of the calling cell.
`static java.lang.Boolean` | `coerceValueToBoolean(ValueEval ve, boolean stringsAreBlanks)`
`static double` | `coerceValueToDouble(ValueEval ev)` Applies some conversion rules if the supplied value is not already a number.
`static int` | `coerceValueToInt(ValueEval ev)` Applies some conversion rules if the supplied value is not already an integer. Value is first coerced to a `double` ( See `coerceValueToDouble()` ).
`static java.lang.String` | `coerceValueToString(ValueEval ve)`
`static ValueEval` | `getSingleValue(ValueEval arg, int srcCellRow, int srcCellCol)` Retrieves a single value from a variety of different argument types according to standard Excel rules.
`static java.lang.Double` | `parseDouble(java.lang.String pText)` Converts a string to a double using standard rules that Excel would use. Tolerates leading and trailing spaces, Doesn't support currency prefixes, commas, percentage signs or arithmetic operations strings.

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Method Detail

### getSingleValue

    public static ValueEval getSingleValue(ValueEval arg,
                                           int srcCellRow,
                                           int srcCellCol)
                                    throws EvaluationException

  Retrieves a single value from a variety of different argument types according to standard Excel rules. Does not perform any type conversion.

  Parameters:
    `arg` - the evaluated argument as passed to the function or operator.
    `srcCellRow` - used when arg is a single column AreaRef
    `srcCellCol` - used when arg is a single row AreaRef
  Returns:
    a `NumberEval`, `StringEval`, `BoolEval` or `BlankEval`. Never `null` or `ErrorEval`.
  Throws:
    `EvaluationException(#VALUE!)` - if srcCellRow or srcCellCol do not properly index into an AreaEval. If the actual value retrieved is an ErrorEval, a corresponding EvaluationException is thrown.
    `EvaluationException`

### chooseSingleElementFromArea

    public static ValueEval chooseSingleElementFromArea(AreaEval ae,
                                                        int srcCellRow,
                                                        int srcCellCol)
                                                 throws EvaluationException

  Implements (some perhaps not well known) Excel functionality to select a single cell from an area depending on the coordinates of the calling cell. Here is an example demonstrating both selection from a single row area and a single column area in the same formula.

  | A | B | C | D
  --- | --- | --- | --- | ---
  1 | 15 | 20 | 25 |
  2 |  |  |  | 200
  3 |  |  |  | 300
  3 |  |  |  | 400

  If the formula "=1000+A1:B1+D2:D3" is put into the 9 cells from A2 to C4, the spreadsheet will look like this:

  | A | B | C | D
  --- | --- | --- | --- | ---
  1 | 15 | 20 | 25 |
  2 | 1215 | 1220 | #VALUE! | 200
  3 | 1315 | 1320 | #VALUE! | 300
  4 | #VALUE! | #VALUE! | #VALUE! | 400

  Note that the row area (A1:B1) does not include column C and the column area (D2:D3) does not include row 4, so the values in C1(=25) and D4(=400) are not accessible to the formula as written, but in the 4 cells A2:B3, the row and column selection works ok.

  The same concept is extended to references across sheets, such that even multi-row, multi-column areas can be useful.

  Of course with carefully (or carelessly) chosen parameters, cyclic references can occur and hence this method can throw a 'circular reference' EvaluationException. Note that this method does not attempt to detect cycles. Every cell in the specified Area `ae` has already been evaluated prior to this method call. Any cell (or cells) part of `ae` that would incur a cyclic reference error if selected by this method, will already have the value ErrorEval.CIRCULAR_REF_ERROR upon entry to this method. It is assumed logic exists elsewhere to produce this behaviour.

  Returns:
    whatever the selected cell's evaluated value is. Never `null`. Never `ErrorEval`.
  Throws:
    `EvaluationException` - if there is a problem with indexing into the area, or if the evaluated cell has an error.

### coerceValueToInt

    public static int coerceValueToInt(ValueEval ev)
                                throws EvaluationException

  Applies some conversion rules if the supplied value is not already an integer.
  Value is first coerced to a `double` ( See `coerceValueToDouble()` ). Note - `BlankEval` is converted to `0`.

  Excel typically converts doubles to integers by truncating toward negative infinity.
  The equivalent java code is:
  `return (int)Math.floor(d);`
  not:
  `return (int)d; // wrong - rounds toward zero`

  Throws:
    `EvaluationException`

### coerceValueToDouble

    public static double coerceValueToDouble(ValueEval ev)
                                      throws EvaluationException

  Applies some conversion rules if the supplied value is not already a number. Note - `BlankEval` is converted to `NumberEval.ZERO`.

  Parameters:
    `ev` - must be a `NumberEval`, `StringEval`, `BoolEval` or `BlankEval`
  Returns:
    actual, parsed or interpreted double value (respectively).
  Throws:
    `EvaluationException(#VALUE!)` - only if a StringEval is supplied and cannot be parsed as a double (See `parseDouble()` for allowable formats).
    `java.lang.RuntimeException` - if the supplied parameter is not `NumberEval`, `StringEval`, `BoolEval` or `BlankEval`
    `EvaluationException`

### parseDouble

    public static java.lang.Double parseDouble(java.lang.String pText)

  Converts a string to a double using standard rules that Excel would use.
  Tolerates leading and trailing spaces,

  Doesn't support currency prefixes, commas, percentage signs or arithmetic operations strings. Some examples:
  " 123 " -> 123.0
  ".123" -> 0.123
  "1E4" -> 1000
  "-123" -> -123.0
  These not supported yet:
  " $ 1,000.00 " -> 1000.0
  "$1.25E4" -> 12500.0
  "5**2" -> 500
  "250%" -> 2.5

  Returns:
    `null` if the specified text cannot be parsed as a number

### coerceValueToString

    public static java.lang.String coerceValueToString(ValueEval ve)

  Parameters:
    `ve` - must be a `NumberEval`, `StringEval`, `BoolEval`, or `BlankEval`
  Returns:
    the converted string value. never `null`

### coerceValueToBoolean

    public static java.lang.Boolean coerceValueToBoolean(ValueEval ve,
                                                         boolean stringsAreBlanks)
                                                  throws EvaluationException

  Returns:
    `null` to represent blank values
  Throws:
    `EvaluationException` - if ve is an ErrorEval, or if a string value cannot be converted

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