User Reference:Expression Syntax - Revision history

Mellinger: /* Signal Values */

2025-07-07T17:12:03Z

Signal Values

← Older revision		Revision as of 17:12, 7 July 2025
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	will address a channel labeled "CPz", and a physical sample position 10ms from the epoch begin when defined for the signal in question.		will address a channel labeled "CPz", and a physical sample position 10ms from the epoch begin when defined for the signal in question.
	(Note: In previous versions of BCI2000 (previous to the Apr 2008 build, up to source revision 1914), expressions used ''zero-based'' indices; you may have to update your configuration accordingly when using expressions that involve signals.)		(Note: In previous versions of BCI2000 (previous to the Apr 2008 build, up to source revision 1914), expressions used ''zero-based'' indices; you may have to update your configuration accordingly when using expressions that involve signals.)

			In some contexts, such as the ''ExpressionFilter'' or ''Operator Watches'', a signal expression without element index may make sense. There, the element index will be amended by the current sample index, or 1 if not available. In this respect, an expression without an element index is similar to a plain state expression.

	====Semicolon====		====Semicolon====

Mellinger: /* States */

2023-01-13T14:36:22Z

States

← Older revision		Revision as of 14:36, 13 January 2023
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	<pre>MyState.AsFloat()</pre>		<pre>MyState.AsFloat()</pre>
	A signed integer is returned by		A signed integer is returned by
	<pre>MyState.AsSigned()</pre>.		<pre>MyState.AsSigned()</pre>
	For clarity, you may also use		For clarity, you may also use
	<pre>MyState.AsUnsigned()</pre>		<pre>MyState.AsUnsigned()</pre>

Mellinger: /* States */

2023-01-13T14:35:48Z

States

← Older revision		Revision as of 14:35, 13 January 2023
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	When assigning to state variables, always use		When assigning to state variables, always use
	<pre>State(ResultCode):=3</pre>		<pre>State(ResultCode):=3</pre>

			By default, the contents of a state variable are interpreted as unsigned integers.
			To interpret the value of a state as a floating-point value, write
			<pre>MyState.AsFloat()</pre>
			A signed integer is returned by
			<pre>MyState.AsSigned()</pre>.
			For clarity, you may also use
			<pre>MyState.AsUnsigned()</pre>
			but it will have no effect, as unsigned is the default.

	====Signal Values====		====Signal Values====

Swiftj: /* Examples */

2022-05-02T19:53:56Z

Examples

← Older revision		Revision as of 19:53, 2 May 2022
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	(ResultCode==TargetCode)?ResultCode:0		(ResultCode==TargetCode)?ResultCode:0
	*A mapping of TargetCode values to arbitrary numbers:		*A mapping of TargetCode values to arbitrary numbers:
	(TargetCode==0)?3:(TargetCode==1)?-4:(TargetCode==2)?18:0		(TargetCode==0)?3:((TargetCode==1)?-4:((TargetCode==2)?18:0))

	===Caveats===		===Caveats===

Mellinger: /* Built-in Functions */

2016-03-18T16:15:02Z

Built-in Functions

← Older revision		Revision as of 16:15, 18 March 2016
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	Arguments and behavior of those functions agree with their implementations in the standard C library.		Arguments and behavior of those functions agree with their implementations in the standard C library.
	In addition, the following functions are provided which are not present the standard C library:		In addition, the following functions are provided which are not present the standard C library:
	:<tt>bits(value, position, count)</tt> converts <tt>value</tt> to a 64 bit unsigned integer, and extracts <tt>count</tt> bits starting at bit <tt>position</tt>. Bits are counted from least to most significant, starting at zero.		:<tt>bits(value, position, count)</tt> converts <tt>value</tt> to a 64 bit unsigned integer, and extracts <tt>count</tt> bits starting at bit <tt>position</tt>. Bits are counted from least to most significant, starting at zero. The result is a number between zero and 2^<tt>count</tt>-1.
	:<tt>bit(value, position)</tt> computes the result of <tt>bits(value, position, 1)</tt> in a slightly more efficient way.		:<tt>bit(value, position)</tt> computes the result of <tt>bits(value, position, 1)</tt> in a slightly more efficient way.

Mellinger: /* Built-in Functions */

2016-03-18T16:12:49Z

Built-in Functions

← Older revision		Revision as of 16:12, 18 March 2016
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	:asin, acos, atan, atan2		:asin, acos, atan, atan2
	:sinh, cosh, tanh		:sinh, cosh, tanh
			Arguments and behavior of those functions agree with their implementations in the standard C library.
			In addition, the following functions are provided which are not present the standard C library:
			:<tt>bits(value, position, count)</tt> converts <tt>value</tt> to a 64 bit unsigned integer, and extracts <tt>count</tt> bits starting at bit <tt>position</tt>. Bits are counted from least to most significant, starting at zero.
			:<tt>bit(value, position)</tt> computes the result of <tt>bits(value, position, 1)</tt> in a slightly more efficient way.

	By deriving from the <tt>Expression</tt> class, a programmer may support additional functions from his own code.		By deriving from the <tt>Expression</tt> class, a programmer may support additional functions from his own code.

Mellinger at 11:27, 22 August 2012

2012-08-22T11:27:16Z

← Older revision		Revision as of 11:27, 22 August 2012
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	Expression syntax tries to be intuitive and is based on C and Matlab notation.		Expression syntax tries to be intuitive and is based on C and Matlab notation.

	===~~Syntactic Elements~~===		===Syntax===
			====Empty Expression====
			The empty expression is a valid expression, and evaluates to 0.

	===="Real" Numbers====		===="Real" Numbers====
	Numbers may be given as literals in decimal or scientific notation:		Numbers may be given as literals in decimal or scientific notation:
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	====Semicolon====		====Semicolon====
	The semicolon may be used to concatenate multiple statements and expressions into a single expression. The expression will then evaluate to the value of the last statement or expression. Examples:		The semicolon may be used to concatenate multiple statements and expressions into a single expression. The expression will then evaluate to the value of the last statement or expression. Examples:
	The expression "4;5" evaluates to 5; the expression "x:=4; y:=3;" evaluates to 3.		The expression "4;5" evaluates to 5; the expression "x:=4; y:=3;" evaluates to 3; the expression ";" evaluates to 0; the expression "1;" evaluates to 1.

	====Comments====		====Comments====

Mellinger: /* States */

2011-11-26T14:24:43Z

States

← Older revision		Revision as of 14:24, 26 November 2011
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	or		or
	<pre>(TargetCode-1)*ResultCode</pre>		<pre>(TargetCode-1)*ResultCode</pre>
	When a variable exists with the same name as a state, the ~~variable~~ takes precedence. To address states unambiguously, use		When a variable exists with the same name as a state, the state takes precedence. To address states unambiguously, use
	<pre>State(TargetCode)==State(ResultCode)</pre>		<pre>State(TargetCode)==State(ResultCode)</pre>
	When assigning to state variables, always use		When assigning to state variables, always use

Mellinger: /* Comments */

2011-11-25T12:32:34Z

Comments

← Older revision		Revision as of 12:32, 25 November 2011
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	will address a channel labeled "CPz", and a physical sample position 10ms from the epoch begin when defined for the signal in question.		will address a channel labeled "CPz", and a physical sample position 10ms from the epoch begin when defined for the signal in question.
	(Note: In previous versions of BCI2000 (previous to the Apr 2008 build, up to source revision 1914), expressions used ''zero-based'' indices; you may have to update your configuration accordingly when using expressions that involve signals.)		(Note: In previous versions of BCI2000 (previous to the Apr 2008 build, up to source revision 1914), expressions used ''zero-based'' indices; you may have to update your configuration accordingly when using expressions that involve signals.)

			====Semicolon====
			The semicolon may be used to concatenate multiple statements and expressions into a single expression. The expression will then evaluate to the value of the last statement or expression. Examples:
			The expression "4;5" evaluates to 5; the expression "x:=4; y:=3;" evaluates to 3.

	====Comments====		====Comments====

Mellinger: /* Signal Values */

2011-11-25T12:27:14Z

Signal Values

← Older revision		Revision as of 12:27, 25 November 2011
Line 67:		Line 67:
	will address a channel labeled "CPz", and a physical sample position 10ms from the epoch begin when defined for the signal in question.		will address a channel labeled "CPz", and a physical sample position 10ms from the epoch begin when defined for the signal in question.
	(Note: In previous versions of BCI2000 (previous to the Apr 2008 build, up to source revision 1914), expressions used ''zero-based'' indices; you may have to update your configuration accordingly when using expressions that involve signals.)		(Note: In previous versions of BCI2000 (previous to the Apr 2008 build, up to source revision 1914), expressions used ''zero-based'' indices; you may have to update your configuration accordingly when using expressions that involve signals.)

			====Comments====
			Expressions support C++-style comments. Beginning with two slashes, a comment extends to the end of a line:
			<pre>Result:=PreviousTargetCode-State(TargetCode); // Compute the return value
			PreviousTargetCode:=State(TargetCode); // Store the target code
			Result; // Return the result</pre>

	===Examples===		===Examples===