qtype_calculated_variable_substituter Class Reference

This class holds the current values of all the variables used by a calculated question. More...

Public Member Functions
	__construct (array $values, $decimalpoint)
	Constructor. More...
	calculate ($expression)
	Evaluate an expression using the variable values. More...
	format_float ($x, $length=null, $format=null)
	Display a float properly formatted with a certain number of decimal places. More...
	get_values ()
	Return an array of the variables and their values. More...
	replace_expressions_in_text ($text, $length=null, $format=null)
	Replace any embedded variables (like {a}) or formulae (like {={a} + {b}}) in some text with the corresponding values. More...

Protected Member Functions
	calculate_raw ($expression)
	Evaluate an expression after the variable values have been substituted. More...
	substitute_values_for_eval ($expression)
	Substitute variable placehodlers like {a} with their value wrapped in (). More...
	substitute_values_pretty ($text)
	Substitute variable placehodlers like {a} with their value without wrapping the value in anything. More...

Protected Attributes
string	$decimalpoint
	character to use for the decimal point in displayed numbers.
array	$prettyvalue
	variable values, with negative numbers wrapped in (...). More...
array	$safevalue
	variable values, with negative numbers wrapped in (...). More...
array	$search
	variable names wrapped in {...}. More...
array	$values
	variable name => value

Detailed Description

This class holds the current values of all the variables used by a calculated question.

It can compute formulae using those values, and can substitute equations embedded in text.

Copyright

2011 The Open University

License

http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

Constructor & Destructor Documentation

__construct()

qtype_calculated_variable_substituter::__construct	(	array	$values,
			$decimalpoint
	)

Constructor.

Parameters

array

$values

variable name => value.

Member Function Documentation

calculate()

qtype_calculated_variable_substituter::calculate

(

$expression

)

Evaluate an expression using the variable values.

Parameters

string

$expression

the expression. A PHP expression with placeholders like {a} for where the variables need to go.

Return values

float

the computed result.

calculate_raw()

qtype_calculated_variable_substituter::calculate_raw (   $expression )

protected

Evaluate an expression after the variable values have been substituted.

Parameters

string

$expression

the expression. A PHP expression with placeholders like {a} for where the variables need to go.

Return values

float

the computed result.

format_float()

qtype_calculated_variable_substituter::format_float	(		$x,
			$length = null,
			$format = null
	)

Display a float properly formatted with a certain number of decimal places.

Parameters

number	$x	the number to format
int	$length	restrict to this many decimal places or significant figures. If null, the number is not rounded.
	int	format 1 => decimalformat, 2 => significantfigures.

Return values

string

formtted number.

get_values()

qtype_calculated_variable_substituter::get_values

(

)

Return an array of the variables and their values.

Return values

array

name => value.

replace_expressions_in_text()

qtype_calculated_variable_substituter::replace_expressions_in_text	(		$text,
			$length = null,
			$format = null
	)

Replace any embedded variables (like {a}) or formulae (like {={a} + {b}}) in some text with the corresponding values.

Parameters

string

$text

the text to process.

Return values

string

the text with values substituted.

substitute_values_for_eval()

qtype_calculated_variable_substituter::substitute_values_for_eval (   $expression )

protected

Substitute variable placehodlers like {a} with their value wrapped in ().

Parameters

string

$expression

the expression. A PHP expression with placeholders like {a} for where the variables need to go.

Return values

string

the expression with each placeholder replaced by the corresponding value.

substitute_values_pretty()

qtype_calculated_variable_substituter::substitute_values_pretty (   $text )

protected

Substitute variable placehodlers like {a} with their value without wrapping the value in anything.

Parameters

string

$text

some content with placeholders like {a} for where the variables need to go.

Return values

string

the expression with each placeholder replaced by the corresponding value.

Member Data Documentation

$prettyvalue

array qtype_calculated_variable_substituter::$prettyvalue

protected

variable values, with negative numbers wrapped in (...).

Used by substitute_values().

$safevalue

array qtype_calculated_variable_substituter::$safevalue

protected

variable values, with negative numbers wrapped in (...).

Used by substitute_values().

$search

array qtype_calculated_variable_substituter::$search

protected

variable names wrapped in {...}.

Used by substitute_values().

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The documentation for this class was generated from the following file:

• question/type/calculated/question.php