WikiSysop at 00:15, 13 December 2017

2017-12-13T00:15:47Z

← Older revision		Revision as of 20:15, 12 December 2017
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	<h1>{quad}EC - Execute Controlled</h1>		<h1>{quad}EC - Execute Controlled</h1>
	{{BoxStart\|⎕EC		{{BoxStart\|<apll>⎕EC</apll>
	\| Execute Controlled "for a string expression"}}		\| Execute Controlled "for a string expression"}}
	{{BoxEnd\|~~Z ← ⎕EC~~ R   <i>~~where argument~~ R is a string expression and returned ~~'''~~Z~~'''~~ is a 3-element [mixed, nested] vector.~~</i>~~}}		{{BoxEnd\|<apll>Z←⎕EC R</apll>   where argument <apll>R</apll> is a string expression and returned <apll>Z</apll> is a 3-element [mixed, nested] vector.}}

	==Monadic Function==		==Monadic Function==
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	<td></td>		<td></td>
	<td></td>		<td></td>
	<td>"R" is executed, and the result Z is a 3-item ~~returned~~ vector.</td>		<td><apll>R</apll> is executed, and the result <apll>Z</apll> is a 3-item vector.</td>
	</tr>		</tr>
	</table>		</table>
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	</tr>		</tr>
	<tr>		<tr>
	<td>R should be a string expression. ⎕EC is frequently used for testing and debugging purposes.</td>		<td><apll>R</apll> should be a string expression. <apll>⎕EC</apll> is frequently used for testing and debugging purposes.</td>
	</tr>		</tr>

	</table>		</table>
	<br />		<br />
	Return codes for Z: Normally, the ~~'''~~first element~~'''~~ of the return code (in variable ~~'''~~Z~~'''~~) represents an integer in the range 0 to 5, where:<br>		Return codes for <apll>Z</apll>: Normally, the first element of the return code (in variable <apll>Z</apll>) represents an integer in the range 0 to 5, where:<br>
	0 = Error<br>		0 = Error<br>
	1 = Expression with a result which would display (for debugging purposes this means '''OK''', ~~'''~~R~~'''~~ was '''not''' problematic.<br>		1 = Expression with a result which would display (for debugging purposes this means '''OK''', <apll>R</apll> was '''not''' problematic.<br>
	2 = Expression with a result which would not display<br>		2 = Expression with a result which would not display<br>
	3 = Expression with no explicit result<br>		3 = Expression with no explicit result<br>
	4 = Branch to a line<br>		4 = Branch to a line<br>
	5 = ~~Simple~~ goto / branch<br><br>		5 = Niladic goto / branch<br><br>
	The second item in Z (returned) is the value that would be returned by ⎕ET (quad event type, without altering the current value of ⎕ET). The third item returned is the actual result ('''IF''' one is generated); for return code 3 or 5 the third item is 0 0⍴0; for return code 4 the third item is the argument to the branch; for return code 0 the third item is ⎕EM.		The second item in <apll>Z</apll> (returned) is the value that would be returned by <apll>⎕ET</apll> (quad event type, without altering the current value of <apll>⎕ET</apll>). The third item returned is the actual result ('''IF''' one is generated); for return code 3 or 5 the third item is <apll>0 0⍴0</apll>; for return code 4 the third item is the argument to the branch; for return code 0 the third item is <apll>⎕EM</apll>.
	<br><br>		<br><br>

	'''Quad Execute Controlled ⎕EC''' sample ''monadic'' calls:		'''Quad Execute Controlled <apll>⎕EC</apll>''' sample ''monadic'' calls:
	<pre>		<pre>
	Z←⎕EC 'a÷1' ⍝ Right argument FAILS(a÷1, because variable "a" does NOT exist).		Z←⎕EC 'a÷1' ⍝ Right argument FAILS(a÷1, because variable "a" does NOT exist).
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	<br><br>		<br><br>
	See also: ~~'''~~[[System_Function_EA\|⎕EA]]~~'''~~<br><br>		See also: [[System_Function_EA\|<apll>⎕EA</apll>]]<br><br>

	{{System Variables}}		{{System Variables}}
	{{Article footer}}		{{Article footer}}

Robert Wallick: created quad EC page

2015-07-31T02:57:12Z

created quad EC page

New page

<h1>{quad}EC - Execute Controlled</h1>
{{BoxStart|⎕EC
| Execute Controlled "for a string expression"}}
{{BoxEnd|Z ← ⎕EC R   <i>where argument R is a string expression and returned '''Z''' is a 3-element [mixed, nested] vector.</i>}}

==Monadic Function==

<table border="1" cellpadding="5" cellspacing="0" rules="none" summary="">
<tr>
<td>
<table border="0" cellpadding="5" cellspacing="0" summary="">
<tr>
<td valign="top"><apll>Z←⎕EC R</apll></td>
<td></td>
<td></td>
<td>"R" is executed, and the result Z is a 3-item returned vector.</td>
</tr>
</table>
</td>
</tr>
<tr>
<td>R should be a string expression. ⎕EC is frequently used for testing and debugging purposes.</td>
</tr>

</table>
<br />
Return codes for Z: Normally, the '''first element''' of the return code (in variable '''Z''') represents an integer in the range 0 to 5, where:<br>
0 = Error<br>
1 = Expression with a result which would display (for debugging purposes this means '''OK''', '''R''' was '''not''' problematic.<br>
2 = Expression with a result which would not display<br>
3 = Expression with no explicit result<br>
4 = Branch to a line<br>
5 = Simple goto / branch<br><br>
The second item in Z (returned) is the value that would be returned by ⎕ET (quad event type, without altering the current value of ⎕ET). The third item returned is the actual result ('''IF''' one is generated); for return code 3 or 5 the third item is 0 0⍴0; for return code 4 the third item is the argument to the branch; for return code 0 the third item is ⎕EM.
<br><br>

'''Quad Execute Controlled ⎕EC''' sample ''monadic'' calls:
<pre>
Z←⎕EC 'a÷1' ⍝ Right argument FAILS(a÷1, because variable "a" does NOT exist).
⍴Z
3 ⍝ Thus a standard 3-element vector has been returned in Z
Z ⍝ Let's see what Z looks like:
0 0 0 VALUE ERROR
⍎ a÷1
∧
Z[1] ⍝ first element in Z is the return code, a zero was generated in this case, indicating an error, as listed above.
0
Z[2]
0 0
Z[3] ⍝ third element returned in Z is the actual nested string error message.
VALUE ERROR
⍎ a÷1
∧

⍝ A different test with "no problems" example:
Z←⎕EC '6÷0.5' ⍝ RIGHT argument SUCCEEDS(6÷0.5) because 6 can be divided by 0.5; under normal circumstances the answer would be 12.
⍴Z
3
Z
1 0 0 12
Z[1] ⍝ first element in Z is the return code, a one was generated in this case, indicating no problem, as per the list above.
1 ⍝ again, 1 = success, no problems encountered
Z[2]
0 0
Z[3]
12 ⍝ And Z[3] correctly holds the expected answer.
</pre>

The '''Execute Controlled''' system function normally takes a string as its right argument.
In particular the left argument string may normally:
* call a function
* jump to a particular label
* perform ANY allowed APL operation (e.g. addition, multiplication, division, subtraction, floor, ceiling, logic test, etc...)
* assign/set a value

<br><br>
See also: '''[[System_Function_EA|⎕EA]]'''<br><br>

{{System Variables}}
{{Article footer}}

System Function EC - Revision history

WikiSysop at 00:15, 13 December 2017

Robert Wallick: created quad EC page