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[[ LCB Docs ]] Add documentation for LiveCode Builder language features
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docs/builder/control_st.lcdoc renamed to docs/builder/language.lcdoc

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Library: control structures
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Library: com.livecode.language
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Name: If
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@@ -187,6 +187,161 @@ Step(number): The value by which to increase or decrease the <Counter>
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StatementList: A set of statements.
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Example:
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public handler Factorial(in pOperand as integer) as number
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if pOperand < 1 then
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return 0
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end if
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variable tTotal as number
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put 1 into tTotal
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variable tCounter as integer
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repeat with tCounter from 1 up to pOperand
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multiply tTotal by tCounter
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end repeat
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return tCounter
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end handler
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Description:
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Use the repeat with <Counter> structure to execute a set of statements until the value of <Counter> reaches or crosses (depending on iteration direction) the value of <Finish>. The counter is increased (or decreased) by <Step> on each iteration of the loop.
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Name: NextRepeat
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Type: control structure
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Summary: Begin the next iteration of a repeat loop.
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Syntax: exit repeat
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Example:
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variable tList as list
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variable tElement
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put [1, 2, 3, "a", 4, "b", 5] into tList
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variable tSum as number
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put 0 into tSum
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repeat for each element tElement in tList
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if tElement is not a number then
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next repeat
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end if
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add tElement to tSum
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end repeat
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Description:
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Use <NextRepeat|next repeat> to skip to the next iteration of a repeat loop. This is particularly useful when operations are only to be performed on iterands which satisfy certain criteria.
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Name: ExitRepeat
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Type: control structure
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Summary: Exit a repeat loop.
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Syntax: exit repeat
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Example:
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public handler ListUpToSentinel(in pList as list, in pSentinel as string) as list
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variable tElement
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variable tNewList as list
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put the empty list into tNewList
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repeat for each element tElement in pList
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if tElement is a string and tElement is pSentinel then
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exit repeat
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end if
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push tElement onto tNewList
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end repeat
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return tNewList
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end handler
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Description:
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Use <ExitRepeat|exit repeat> to exit a repeat loop, for example when a certain condition is met.
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Name: Return
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Type: statement
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Syntax: return [<returnValue>]
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Summary: Causes execution of the current handler to end, and control return to the caller.
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Parameters:
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returnValue (any): The value to return
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Description:
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Use the return control structure to halt execution of the current handler, to return control to the caller, and optionally to return a value.
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Note: It is a checked runtime error for a value returned from a handler to not match the return type of the handler it is in.
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Name: ThrowError
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Type: statement
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Syntax: throw <errorString>
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Summary: Causes an error to be raised.
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Parameters:
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errorString (string): The error to throw.
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Example:
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variable tVar as optional number
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put "Z" parsed as string into tVar
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if tVar is not defined then
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throw tVar && "is not a number
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end if
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Description:
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The throw statement causes an error to be raised. This causes execution to terminate, and the error is passed back to environment.
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The Error expression must be an expression that evaluates to a string.
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Note: There is currently no try / catch mechanism in LiveCode Builder, so throwing an error will cause the error to be raised in LiveCode Script in the appropriate context.
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Name: PutInto
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Type: statement
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Summary: Put a value into a container.
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Syntax: put <sourceValue> into <targetContainer>
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Parameters:
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sourceValue (any): The value to put into the <targetContainer>
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targetContainer (any): A valid target for <sourceValue>
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Description:
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Assigns the result of evaluating <sourceValue> to <targetContainer>.
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>*Note:* It is a checked runtime error for the source value's type to not be compatible with the target expression's type.
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Name: SetTo
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Type: statement
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Summary: Put a value into a container.
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Syntax: set <targetContainer> to <sourceValue>
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Parameters:
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targetContainer (any): A valid target for <sourceValue>
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sourceValue (any): The value to put into the <targetContainer>
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Description:
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Assigns the result of evaluating <sourceValue> to <targetContainer>.
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>*Note:* It is a checked runtime error for the source value's type to not be compatible with the target expression's type.
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Name: Get
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Type: statement
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Summary: Evaluate an expression and put it into the result.
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Syntax: get <expression>
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Parameters:
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expression: Any expression.
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Description:
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Use the repeat with <Counter> structure to execute a set of statements until the value of <Counter> reaches or crosses (depending on iteration direction) the value of <Finish>. The counter is increased (or decreased) by <Step> on each iteration of the loop.
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The get statement evaluates the Value expression and returns it as the result of the statement. The value is subsequently available by using <TheResult|the result> expression.
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References: TheResult(expression)
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Name: TheResult
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Type: expression
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Summary: The result of the previous statement.
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Syntax: the result
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Example:
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resolve script object "this stack"
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get property "name" of the result
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log the result
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Example:
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get 20
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subtract 1 from the result
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divide the result by 2
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round the result
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-- the result is 10
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Description:
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Use <TheResult|the result> to obtain the return value of the previous (executed) non-control structure statement.
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>*Note:* Result expressions are not assignable.
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