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80 lines
4.6 KiB
Markdown
80 lines
4.6 KiB
Markdown
---
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hide_title: true
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hide_table_of_contents: true
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title: Expression
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---
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<##head##>
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# Expression
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This node enables you to do your own calculations using simple expressons. Inputs are automatically derived from the expression. An expression set to `a + someName + 1` will get two inputs: one for <span className="ndl-data">a</span> and one for <span className="ndl-data">someName</span>.
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<div className="ndl-image-with-background xl">
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</div>
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The <span className="ndl-node">Expression</span> node runs JavaScript under the hood and supports a range of mathematical expressions.
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<##head##>
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## Built in math functions
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Expressions support the following funcitons:
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- `min(a,b)` - Minimum of two values
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- `max(a,b)` - Maximum of two values
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- `cos(angle)` - The cosine of an angle in radians
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- `sin(angle)` - The sine of an angle in radians
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- `tan(angle)` - The tangent of an angle in radians
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- `sqrt(a)` - Square root of a number
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- `pi` - PI in radians
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- `round(a)` - Rounds a number to the closest integer
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- `floor(a)` - Removes the fractional part of a number
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- `ceil(a)` - Rounds a value up to the closest higher integer. E.g. `round(1.1)` equals `2`.
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- `abs(a)` - The absolute value of a number. Negative values will become positive.
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- `random()` - A random number from 0 to 1
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## Advanced
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The _Expression_ node is running JavaScript under the hood so in addition to the above functions any standard
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JavaScript functions will also be valid. The _Expression_ node will add a `return` statement before the
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expression is executed. `1+2` will be evaluated as `return (1+2)`
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## Truthy and Falsy signals
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You can use the signal outputs <span className="ndl-signal">On True</span> and <span className="ndl-signal">On False</span> to trigger actions based on the result of an expression, if the result is considered "truthy" or "falsy" in Javascript.
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Normally, an expression node recalculates whenever one of the input parameters change. However, if you connect a signal to the <span className="ndl-signal">Run</span> signal input you can control when the expression is calculated. It will only calculate and update it's outputs when a signal is received.
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<div className="ndl-image-with-background xl">
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</div>
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## Inputs
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| Data | Description |
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| -------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
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| <span className="ndl-data">Expression</span> | The expression to be calculated. |
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| <span className="ndl-data">Run</span> | Normally the expression is recalucated every time one of the input parameters change. But if you want to control when the expression is calculated you can connect a signal to this input, then the expression will **only** be calculated when a signal is received. |
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### Parameters
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Inputs are automatically derived from the expression. An expression set to `a + someName + 1` will get two inputs, one for `a` and one for `someName`.<br/><br/>As soon as any of the input values changes, the expression is reevaluated.
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## Outputs
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| Data | Description |
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| ---------------------------------------- | --------------------------------------------------------------------------------------------- |
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| <span className="ndl-data">Result</span> | <##output:result##>This output contains the result when evaluating the expression<##output##> |
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| <span className="ndl-data">Is true</span> | <##output:isTrue##>This output will be true if the result of the expression is "truthy", that is considered true in Javascript.<##output##> |
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| <span className="ndl-data">Is false</span> | <##output:isFalse##>This output will be true if the result of the expression is "falsy", that is considered false in Javascript.<##output##> |
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| <span className="ndl-signal">On True</span> | <##output:isTrueEv##>A signal will be sent on this output when the expression is calculated and the result is "truthy".<##output##> |
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| <span className="ndl-signal">On False</span> | <##output:isFalseEv##>A signal will be sent on this output when the expression is calculated and the result is "falsy".<##output##> |
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