System Variable LX: Difference between revisions

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<h1>{quad}LX - Latent Expression</h1>
<h1>{quad}LX - Latent Expression</h1>
{{BoxStart|<apll>Z←⎕LX</apll>
| returns the current value of the Latent eXpression. }}
{{BoxEnd|<apll>Z</apll> is a string containing the current value of ⎕LX, and is null if {quad}LX is not defined. This is the command to execute when the workspace is loaded with )LOAD.}}<br/>


The {quad}LX variable is used within a workspace to set the action to take when the workspace is loaded via )LOAD or the '''File, Open''' menu. Typically {quad}LX is set to the name of a function in the workspace. {quad}LX defaults to null.
{| border="1" cellpadding="5" cellspacing="0" rules="none" summary=""
|| <apll>⎕LX←'START'</apll> ||  Have the workspace execute function START when it is loaded via )LOAD or the '''<u>F</u>ile, <u>O</u>pen''' menu
|-
| valign="top" |<apll>⎕LX←''</apll> || Do not have any function execute when the workspace is loaded (this is the default).
|-
|}
<br />
 
The {quad}LX variable is used within a workspace to set the action to take when the workspace is loaded via )LOAD or the '''<u>F</u>ile, <u>O</u>pen''' menu. Typically {quad}LX is set to the name of a function in the workspace. {quad}LX defaults to null.


Example usage:
Example usage:
:'''<big><code> {quad}LX{:=}'Start'</code></big>'''
:'''<big><code> {quad}LX{:=}'Start'</code></big>'''


When this workspace is saved, the next time it is loaded through the <big>''')LOAD'''</big> command or the '''file, open''' menu, it will attempt to start the function <big>'''Start'''</big>. An error will occur if the function named in <big>'''{quad}LX'''</big> is not present when the workspace is loaded.
When this workspace is saved, the next time it is loaded through the <big>''')LOAD'''</big> command or the '''<u>F</u>ile, <u>O</u>pen''' menu, it will attempt to start the function <big>'''Start'''</big>. An error will occur if the function named in <big>'''{quad}LX'''</big> is not present when the workspace is loaded.


The <big>'''{quad}LX'''</big> function is ''not'' executed if the workspace is loaded via the <apll>)XLOAD</apll> command or through the '''file, xload''' menu.
The <big>'''{quad}LX'''</big> function is ''not'' executed if the workspace is loaded via the <apll>)XLOAD</apll> command or through the '''<u>F</u>ile, <u>X</u>load''' menu.


The function of {quad}LX is similar to the function of the AUTOEXEC.BAT file when DOS is started, or when in Windows if you have a shortcut in the Startup Folder in the Start Menu. The function or action in the {quad}LX system variable is executed before the Session Manager returns control to you.
The function of {quad}LX is similar to the function of the AUTOEXEC.BAT file when DOS is started, or when in Windows if you have a shortcut in the Startup Folder in the Start Menu. The function or action in the {quad}LX system variable is executed before the Session Manager returns control to you.
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The action of <big>'''{quad}LX'''</big> when a workspace is <apll>)LOAD</apll>ed is essentially equivalent to typing <big>'''{execute}{quad}LX'''</big> immediately after loading the workspace.
The action of <big>'''{quad}LX'''</big> when a workspace is <apll>)LOAD</apll>ed is essentially equivalent to typing <big>'''{execute}{quad}LX'''</big> immediately after loading the workspace.


Note that system commands beginning with a <big>''')'''</big> cannot be executed through <big><b>{quad}LX</b></big>. This prevents endless loops, such as if a workspace named <big>'''loop'''</big> had a {quad}LX value of <big>''')load loop'''</big>.
Note that system commands beginning with a <big>''')'''</big> cannot be executed through <big><b>{quad}LX</b></big>. This is different from the APL Standard. This (lack of) functionality prevents endless loops, such as if a workspace named <big>'''loop'''</big> had a {quad}LX value of <big>''')load loop'''</big>.


==See Also==
==See Also==
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{{System Variables}}
{{System Variables}}
{{Article footer}}

Revision as of 13:24, 13 March 2013

⎕LX - Latent Expression

Z←⎕LX returns the current value of the Latent eXpression.
Z is a string containing the current value of ⎕LX, and is null if ⎕LX is not defined. This is the command to execute when the workspace is loaded with )LOAD.


⎕LX←'START' Have the workspace execute function START when it is loaded via )LOAD or the File, Open menu
⎕LX←'' Do not have any function execute when the workspace is loaded (this is the default).


The ⎕LX variable is used within a workspace to set the action to take when the workspace is loaded via )LOAD or the File, Open menu. Typically ⎕LX is set to the name of a function in the workspace. ⎕LX defaults to null.

Example usage:

⎕LX←'Start'

When this workspace is saved, the next time it is loaded through the )LOAD command or the File, Open menu, it will attempt to start the function Start. An error will occur if the function named in ⎕LX is not present when the workspace is loaded.

The ⎕LX function is not executed if the workspace is loaded via the )XLOAD command or through the File, Xload menu.

The function of ⎕LX is similar to the function of the AUTOEXEC.BAT file when DOS is started, or when in Windows if you have a shortcut in the Startup Folder in the Start Menu. The function or action in the ⎕LX system variable is executed before the Session Manager returns control to you.

The action of ⎕LX when a workspace is )LOADed is essentially equivalent to typing ⍎⎕LX immediately after loading the workspace.

Note that system commands beginning with a ) cannot be executed through ⎕LX. This is different from the APL Standard. This (lack of) functionality prevents endless loops, such as if a workspace named loop had a ⎕LX value of )load loop.

See Also

System Variables (A value may be assigned to these except for ⎕DM)
⎕ALX ⎕CT ⎕DM ⎕DT ⎕ELX ⎕FC ⎕FEATURE ⎕FPC ⎕IC ⎕IO
⎕LR ⎕LX ⎕PP ⎕PR ⎕PW ⎕RL ⎕SA ⎕WSID
Niladic System Functions (a value cannot be assigned to these)
⎕A ⎕AV ⎕EM ⎕ET ⎕LC ⎕NNAMES ⎕NNUMS ⎕SI ⎕SYSID ⎕SYSVER
⎕T ⎕TC ⎕TCBEL ⎕TCBS ⎕TCESC ⎕TCFF ⎕TCHT ⎕TCLF ⎕TCNL ⎕TCNUL
⎕TS ⎕WA
Monadic or dyadic system functions (a value cannot be assigned to these)
⎕AT ⎕CR ⎕DC ⎕DFT ⎕DL ⎕DR ⎕EA ⎕EC ⎕ERROR ⎕ES
⎕EX ⎕FMT ⎕FX ⎕MF ⎕NAPPEND ⎕NC ⎕NCREATE ⎕NERASE ⎕NINFO ⎕NL
⎕NLOCK ⎕NREAD ⎕NRENAME ⎕NREPLACE ⎕NRESIZE ⎕NSIZE ⎕NTIE ⎕NUNTIE ⎕STOP ⎕TF
⎕TRACE ⎕UCS ⎕VR
Note that quad functions and variables (except for the ⎕A family of functions) are case insensitive


See Also
System Commands System Variables and Functions Operators


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