CASE
Author: Marco
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Here is a simple function similar to the SWITCH function but a little
more powerful in some situations. The major difference is that SWITCH
selects and executes the block corresponding to a value, whereas CASE
selects the block to execute corresponding to the first condition that is
evaluated to true (not none).
A sample is better than a long explanation:
x: 1 y: 2
case/default [
x > y [print [x "is greater than" y]]
x = y [print [x "is equal to" y]]
x < y [print [x "is less than" y]]
][
print "no true condition"
]
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This could be done with a set of EITHERs, but the CASE function is much
simpler. Here is what the above example would require using EITHER:
x: 1 y: 2
either x > y [
print [x "is greater than" y]
][
either x = y [
print [x "is equal to" y]
][
either x < y [
print [x "is less than" y]
][
print "no true condition"
]
]
]
|
The code to create the CASE function is very simple:
case: func [
"Find a condition and evaluates what follows it."
[throw]
cases [block!] "Block of cases to evaluate."
/default
case "Default case if no others are found."
/local condition body
][
while [not empty? cases][
set [condition cases] do/next cases
if condition [
body: first cases
break
]
cases: next cases
]
if not body [body: any [case]]
do body
]
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