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If condition evaluates to TRUE, then execute all commands in
cmdlist, else execute all commands in cmdlist2.
IF condition THEN command
IF condition THEN { cmdlist }
IF condition THEN command1 ELSE command2
IF condition THEN { cmdlist } ELSE command2
IF condition THEN command1 ELSE { cmdlist2 }
IF condition THEN { cmdlist } ELSE { cmdlist2 }
- condition
A logical expression to be evaluated.
- command cmdlist
A single command (or command list) that is executed
if condition evaluates to TRUE.
- command2 cmdlist2
A single command (or command list) that is executed if
condition evaluates to FALSE.
Note that in nested IF-THEN-ELSE clauses, the first ELSE
clause always matches the first IF clause. This is
different from the conventions of most compilers, and it may not be intuitive.
Explicit use of {cmdlists} is recommended in these nested
cases.
%cmdebug > if [q-3]>[db+4] then c
If the contents of Q-3 are greater than the contents of DB+4, then continue.
$nmdebug > if (length>20) and (pcsf=a) then {wl "GOT IT"; c}
If the value of the variable length is greater than 20, and the
contents of the predefined variable pcsf equals $a, then execute the
following from the command list: print the string "GOT IT", then continue.
$nmdat > if 1 then {if 0 then wl "wee" else wl "willy"} else wl "wonka"
willy
This example shows a nested IF-THEN-ELSE clause within a
cmdlist clause.
The interpreter does not parse or analyze the contents of the clauses prior to
their execution. Based on the value of the condition, the THEN or
ELSE clause is be executed, and the other clause disregarded.
This implies that the clauses may be syntactically illegal, but the errors are
not discovered until they are executed.
Note that in the following examples, entire clauses are bogus, but not detected:
$nmdebug > if TRUE then wl "good" else XXXXXXXXXXXXXXXXXX
good
$nmdebug > if FALSE then XXXXXXXXXXXXXXXX else wl "good"
good
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