Control Structures - Revision history

WikiSysop: /* Overview */

2024-03-16T00:24:15Z

Overview

← Older revision		Revision as of 20:24, 15 March 2024
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	<td></td>		<td></td>
	<td></td>		<td></td>
	<td>Repeatedly execute the statements between <apll>:repeat</apll> and <apll>:until</apll> until <i>expr</i> is <apll>0</apll>.</td>		<td>Repeatedly execute the statements between <apll>:repeat</apll> and <apll>:until</apll> until <i>expr</i> is <apll>1</apll>.</td>
	</tr>		</tr>

Paul Robinson: t/c

2019-10-13T22:53:51Z

t/c

← Older revision		Revision as of 18:53, 13 October 2019
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	[[Category;Examples]]		[[Category:Examples]]

Paul Robinson: /* WHILE Statement */

2019-10-13T22:52:50Z

WHILE Statement

← Older revision		Revision as of 18:52, 13 October 2019
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	To interrupt the flow of control within a block of statements, use the <apll>:continue</apll> or <apll>:leave</apll> keywords. The former keyword transfers control to the end of the block continuing with the next repetition, skipping the statements between the <apll>:continue</apll> and matching <apll>:endwhile</apll> or <apll>:until</apll> keywords, but evaluating and acting upon an <apll>:until</apll> statement, if present. The latter keyword exits the <apll>:while</apll> loop entirely and transfers control to the statement after the matching <apll>:endwhile</apll> or <apll>:until</apll> statement. Typically, these two keywords appear within <apll>:if</apll> statements.		To interrupt the flow of control within a block of statements, use the <apll>:continue</apll> or <apll>:leave</apll> keywords. The former keyword transfers control to the end of the block continuing with the next repetition, skipping the statements between the <apll>:continue</apll> and matching <apll>:endwhile</apll> or <apll>:until</apll> keywords, but evaluating and acting upon an <apll>:until</apll> statement, if present. The latter keyword exits the <apll>:while</apll> loop entirely and transfers control to the statement after the matching <apll>:endwhile</apll> or <apll>:until</apll> statement. Typically, these two keywords appear within <apll>:if</apll> statements.


			[[Category;Examples]]

Paul Robinson: /* GOTO Statement */

2015-09-11T21:16:02Z

GOTO Statement

← Older revision		Revision as of 17:16, 11 September 2015
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	<apll>:goto <i>expr</i></apll>		<apll>:goto <i>expr</i></apll>

	This statement transfers control to the line number specified in <i>expr</i>. The value of <i>expr</i> must be a numeric simple scalar or one-element vector. This statement is equivalent to <~~apll~~>→<i>expr</i></~~apll~~>.		This statement transfers control to the line number specified in <i>expr</i>. The value of <i>expr</i> must be a numeric simple scalar or one-element vector. This statement is equivalent to <tt>[[→]]<i>expr</i></tt>.

	== IF Statement ==		== IF Statement ==

Robert Wallick: augmented cases branching example

2015-02-22T03:32:18Z

augmented cases branching example

← Older revision		Revision as of 23:32, 21 February 2015
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	<apll>:switch</apll> is an alias for <apll>:select</apll>; in the above discussion wherever <apll>:select</apll> appears, you may substitute <apll>:switch</apll>.		<apll>:switch</apll> is an alias for <apll>:select</apll>; in the above discussion wherever <apll>:select</apll> appears, you may substitute <apll>:switch</apll>.
	<br><br><font color=green><strong>		<br><br><font color=green><strong>
	As an alternative to the above, for a pure original APL solution to Multiple Cases scenarios in a user-function, consider using the following APL control structure~~,<br>~~		== Cases Branching Example 1 ==
	~~for~~ example the following user-function, has one local variable (boolCases) with 6 different cases handled:<br>		As an alternative to the Select/Switch control structure(s) above, for a pure original APL solution to Multiple Cases scenarios in a user-function, consider using the following APL control structure. For example the following <u>user-function</u>, has one local variable (boolCases) with 6 different cases handled:<br>
	<u>BranchingExample1</u>;boolCases<br>		<u>BranchingExample1</u>;boolCases<br>
	[1] ⍝MULTIPLE CASES: Branching/GoTo Example #1<br>		[1] ⍝MULTIPLE CASES: Branching/GoTo Example #1<br>
	[2] boolCases←0 1 1 1 0 0 ⍝Leftmost boolean 1 determines which case or block will be executed<br>		[2] boolCases←0 1 1 1 0 0       ⍝Leftmost boolean 1 determines which case or block will be executed { 0 <u>1</u> 1 1 0 0 }<br>
	[3] →boolCases/(Label1 Label2 Label3 Label4 Label5 Label6)<br>		[3] →boolCases/(Label1 <u>Label2</u> Label3 Label4 Label5 Label6)<br>
	[4] 'Did NOT branch, Case ELSE.'<br>		[4] 'Did NOT branch, Case ELSE.'<br>
	[5] →Next1<br>		[5] →Next1<br>
	[6] Label1: 'Do this, Label1'<br>		[6] Label1: 'Do this, Label1'<br>
	[7] →Next1<br>		[7] →Next1<br>
	[8] Label2: 'Do this, Label2'<br>		[8] <u>Label2</u>: 'Do this, Label2'         ⍝This case <u>will</u> get branched to based on boolCases!<br>
	[9] →Next1<br>		[9] →Next1<br>
	[10] Label3: 'Do this, Label3'<br>		[10] Label3: 'Do this, Label3'<br>
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	[17] Next1: 'Code continues here.'<br>		[17] Next1: 'Code continues here.'<br>
	<br>		<br>
	BranchingExample1<br>		BranchingExample1       ⍝User-session, <u>BranchingExample1</u> ''typed in by user''.<br>
	Do this, Label2<br>		Do this, Label2<br>
	Code continues here.<br>		Code continues here.<br>

Robert Wallick: /* SELECT/SWITCH Statements */

2015-02-17T22:01:37Z

SELECT/SWITCH Statements

← Older revision		Revision as of 18:01, 17 February 2015
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	[1] ⍝MULTIPLE CASES: Branching/GoTo Example #1<br>		[1] ⍝MULTIPLE CASES: Branching/GoTo Example #1<br>
	[2] boolCases←0 1 1 1 0 0 ⍝Leftmost boolean 1 determines which case or block will be executed<br>		[2] boolCases←0 1 1 1 0 0 ⍝Leftmost boolean 1 determines which case or block will be executed<br>
	[3] →boolCases/(Label1, Label2, Label3, Label4, Label5, Label6)<br>		[3] →boolCases/(Label1 Label2 Label3 Label4 Label5 Label6)<br>
	[4] 'Did NOT branch, ~~case~~ ELSE.'<br>		[4] 'Did NOT branch, Case ELSE.'<br>
	[5] →0<br>		[5] →Next1<br>
	[6] Label1: 'Do this, Label1'<br>		[6] Label1: 'Do this, Label1'<br>
	[7] →0<br>		[7] →Next1<br>
	[8] Label2: 'Do this, Label2'<br>		[8] Label2: 'Do this, Label2'<br>
	[9] →0<br>		[9] →Next1<br>
	[10] Label3: 'Do this, Label3'<br>		[10] Label3: 'Do this, Label3'<br>
	[11] →0<br>		[11] →Next1<br>
	[12] Label4: 'Do this, Label4'<br>		[12] Label4: 'Do this, Label4'<br>
	[13] →0<br>		[13] →Next1<br>
	[14] Label5: 'Do this, Label5'<br>		[14] Label5: 'Do this, Label5'<br>
	[15] →0<br>		[15] →Next1<br>
	[16] Label6: 'Do this, Label6'<br>		[16] Label6: 'Do this, Label6'<br>
	[17] →0<br>		[17] Next1: 'Code continues here.'<br>
	<br>		<br>
	BranchingExample1<br>		BranchingExample1<br>
	Do this, Label2<br>		Do this, Label2<br>
			Code continues here.<br>
	</strong></font>		</strong></font>

Robert Wallick: /* SELECT/SWITCH Statements */

2015-02-17T21:35:12Z

SELECT/SWITCH Statements

← Older revision		Revision as of 17:35, 17 February 2015
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	<apll>:switch</apll> is an alias for <apll>:select</apll>; in the above discussion wherever <apll>:select</apll> appears, you may substitute <apll>:switch</apll>.		<apll>:switch</apll> is an alias for <apll>:select</apll>; in the above discussion wherever <apll>:select</apll> appears, you may substitute <apll>:switch</apll>.
			<br><br><font color=green><strong>
			As an alternative to the above, for a pure original APL solution to Multiple Cases scenarios in a user-function, consider using the following APL control structure,<br>
			for example the following user-function, has one local variable (boolCases) with 6 different cases handled:<br>
			<u>BranchingExample1</u>;boolCases<br>
			[1] ⍝MULTIPLE CASES: Branching/GoTo Example #1<br>
			[2] boolCases←0 1 1 1 0 0 ⍝Leftmost boolean 1 determines which case or block will be executed<br>
			[3] →boolCases/(Label1, Label2, Label3, Label4, Label5, Label6)<br>
			[4] 'Did NOT branch, case ELSE.'<br>
			[5] →0<br>
			[6] Label1: 'Do this, Label1'<br>
			[7] →0<br>
			[8] Label2: 'Do this, Label2'<br>
			[9] →0<br>
			[10] Label3: 'Do this, Label3'<br>
			[11] →0<br>
			[12] Label4: 'Do this, Label4'<br>
			[13] →0<br>
			[14] Label5: 'Do this, Label5'<br>
			[15] →0<br>
			[16] Label6: 'Do this, Label6'<br>
			[17] →0<br>
			<br>
			BranchingExample1<br>
			Do this, Label2<br>
			</strong></font>

	== WHILE Statement ==		== WHILE Statement ==

WikiSysop: /* WHILE Statement */

2012-11-16T21:58:14Z

WHILE Statement

← Older revision		Revision as of 17:58, 16 November 2012
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	The expressions must evaluate to a Boolean-valued scalar or one-element vector.		The expressions must evaluate to a Boolean-valued scalar or one-element vector.

	In the righthand form above, the block of statements is executed and then the expression is executed. It must evaluate to a Boolean-valued scalar or one-element vector. If the expression is true, the Control Structure terminates and execution continues with the statement after the <apll>:until</apll> statement; if the expression is false, execution continues at the start of the Control Structure.		In the righthand form above, if the <apll>:while</apll> expression evaluates to a scalar or one-element vector whose value is <apll>1</apll>, the block of statements is executed and then the <apll>:until</apll> expression is executed. It must evaluate to a Boolean-valued scalar or one-element vector. If the <apll>:until</apll> expression is true, the Control Structure terminates and execution continues with the statement after the <apll>:until</apll> statement; if the <apll>:until</apll> expression is false, execution continues at the start of the Control Structure.

	The <apll>:while</apll> statement may be followed by zero or more <apll>:andif</apll> statements to narrow the conditions under which the block of statements is executed, or it may be followed by zero or more <apll>:orif</apll> statements to widen the conditions under which the block of statements is executed. The <apll>:andif</apll> and <apll>:orif</apll> statements may not be mixed after a <apll>:while</apll> statement.		The <apll>:while</apll> statement may be followed by zero or more <apll>:andif</apll> statements to narrow the conditions under which the block of statements is executed, or it may be followed by zero or more <apll>:orif</apll> statements to widen the conditions under which the block of statements is executed. The <apll>:andif</apll> and <apll>:orif</apll> statements may not be mixed after a <apll>:while</apll> statement.

WikiSysop: /* SELECT/SWITCH Statements */

2010-07-07T13:24:34Z

SELECT/SWITCH Statements

← Older revision		Revision as of 09:24, 7 July 2010
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	This statement exits the current function and is equivalent to <apll>→0</apll>.		This statement exits the current function and is equivalent to <apll>→0</apll>.

	== SELECT ~~Statement~~ ==		== SELECT/SWITCH Statements ==

			<table summary="">
			<tr>
			<td>
	<apll>:select <i>expr1</i></apll><br />		<apll>:select <i>expr1</i></apll><br />
	<apll>:case <i>expr2</i></apll><br />		<apll>:case <i>expr2</i></apll><br />
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	... (Block of statements)<br />		... (Block of statements)<br />
	<apll>:endselect</apll>		<apll>:endselect</apll>
			</td>
			<td>   <b>OR</b>   </td>
			<td>
			<apll>:switch <i>expr1</i></apll><br />
			<apll>:case <i>expr2</i></apll><br />
			... (Block of statements)<br />
			<apll>:caselist <i>expr3</i></apll><br />
			... (Block of statements)<br />
			<apll>:else</apll><br />
			... (Block of statements)<br />
			<apll>:endswitch</apll>
			</td>
			</tr>
			</table>

	This statement provides a mechanism for making a choice from multiple cases as to which block of statements is executed. The <apll>:select</apll> statement expression is evaluated and compared against each successive <apll>:case</apll> expression and the successive items in each <apll>:caselist</apll> expression. Control is given to the first block of statements whose corresponding expression (or expression item in the case of <apll>:caselist</apll>) matches the <apll>:select</apll> expression.		This statement provides a mechanism for making a choice from multiple cases as to which block of statements is executed. The <apll>:select</apll> statement expression is evaluated and compared against each successive <apll>:case</apll> expression and the successive items in each <apll>:caselist</apll> expression. Control is given to the first block of statements whose corresponding expression (or expression item in the case of <apll>:caselist</apll>) matches the <apll>:select</apll> expression.
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	Because of the way <apll>:select</apll> statements are executed, a line with a <apll>:case</apll> or <apll>:caselist</apll> statement may not be a branch target; otherwise a <apll>DESTINATION ERROR</apll> is signaled. That is, a <apll>:select</apll> statement may be entered at the top only.		Because of the way <apll>:select</apll> statements are executed, a line with a <apll>:case</apll> or <apll>:caselist</apll> statement may not be a branch target; otherwise a <apll>DESTINATION ERROR</apll> is signaled. That is, a <apll>:select</apll> statement may be entered at the top only.

			<apll>:switch</apll> is an alias for <apll>:select</apll>; in the above discussion wherever <apll>:select</apll> appears, you may substitute <apll>:switch</apll>.

	== WHILE Statement ==		== WHILE Statement ==

WikiSysop: /* Overview */

2010-07-07T13:18:05Z

Overview

← Older revision		Revision as of 09:18, 7 July 2010
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	<td></td>		<td></td>
	<td>Execute a specific block of statements depending upon which <apll>:case</apll> or <apll>:caselist</apll> expression matches <i>expr1</i>.</td>		<td>Execute a specific block of statements depending upon which <apll>:case</apll> or <apll>:caselist</apll> expression matches <i>expr1</i>.</td>
			</tr>

			<tr valign="top">
			<td><apll>:switch <i>expr1</i> ⋄ :case <i>expr2</i> ⋄ </apll>...<apll> </apll><br/> <apll> ⋄ :caselist <i>expr3</i> ⋄ </apll>...<apll> ⋄ :endswitch</apll></td>
			<td></td>
			<td></td>
			<td>Same as <apll>:select</apll>.</td>
	</tr>		</tr>

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	<apll>[3] L1::if I < 10 ⋄ </apll>...</li>		<apll>[3] L1::if I < 10 ⋄ </apll>...</li>

	<li><p>Each Control Structure that closes with a statement-specific keyword (<apll>:endfor</apll>, <apll>:endforlcl</apll>, <apll>:endif</apll>, <apll>:endrepeat</apll>, <apll>:endselect</apll>, and <apll>:endwhile</apll>), may instead close with the <apll>:end</apll> keyword.</p></li>		<li><p>Each Control Structure that closes with a statement-specific keyword (<apll>:endfor</apll>, <apll>:endforlcl</apll>, <apll>:endif</apll>, <apll>:endrepeat</apll>, <apll>:endselect</apll>, <apll>:endswitch</apll>, and <apll>:endwhile</apll>), may instead close with the <apll>:end</apll> keyword.</p></li>
	</ul>		</ul>
	<br />		<br />