Conditional structures: Difference between revisions

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=={{header|langur}}==
=={{header|langur}}==
If and switch expressions always produce a value, even if it's nothing (null).
If and switch expressions always produce a value, even if it's nothing (null). In the shortened forms, you dispense with the keywords (except the first one).

In the shortened forms, you dispense with the keywords (except the first one).


===if expressions===
===if expressions===
If expressions are scoped per section.
If expressions are scoped per section.
<syntaxhighlight lang="langur">if .x == 0 {
<syntaxhighlight lang="langur">if x == 0 {
...
...
} else if .x > 0 {
} else if x > 0 {
val .y = 100
val y = 100
...
...
} else {
} else {
val .y = 70
val y = 70
...
...
}</syntaxhighlight>
}</syntaxhighlight>
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This is more flexible than a ternary operator, as it allows more than one test. An else section is optional (null by default).
This is more flexible than a ternary operator, as it allows more than one test. An else section is optional (null by default).


<syntaxhighlight lang="langur">if(.x > .y: ...; .x < .y: ...; /* else */ ...)</syntaxhighlight>
<syntaxhighlight lang="langur">if(x > y: ...; x < y: ...; /* else */ ...)</syntaxhighlight>


===simple if===
===simple if===
Simple if expressions use a colon after the test condition. This is convenient for simple branching or assignments, without having to use curly braces, but does not allow for else if or else sections.
Simple if expressions use a colon after the test condition. This is convenient for simple branching or assignments, without having to use curly braces, but does not allow for else if or else sections.


<syntaxhighlight lang="langur">if .x > .y: break</syntaxhighlight>
<syntaxhighlight lang="langur">if x > y: break</syntaxhighlight>


===switch expressions===
===switch expressions===
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Switch defaults to testing that any condition is true (as familiar to many programmers), but this can be changed by specifying an infix operator within square brackets, such as switch[and].
Switch defaults to testing that any condition is true (as familiar to many programmers), but this can be changed by specifying an infix operator within square brackets, such as switch[and].


<syntaxhighlight lang="langur">switch .x, .y, .z {
<syntaxhighlight lang="langur">switch x, y, z {
case true: ...
case true: ...
# any are true
# any are true
case false, _: ...
case false, _: ...
# .x == false
# x == false
case _, null, true: ...
case _, null, true: ...
# .y == null or .z == true
# y == null or z == true
case xor _, true, true: ...
case xor _, true, true: ...
# .y == true xor .z == true
# y == true xor z == true
}
}


switch 0 {
switch 0 {
case .x, .y: ...
case x, y: ...
# .x or .y equals 0
# x or y equals 0
...
...
}
}


switch[and] .x, .y, .z {
switch[and] x, y, z {
case true: ...
case true: ...
# all are true
# all are true
case false, _: ...
case false, _: ...
# .x == false
# x == false
case _, null, true: ...
case _, null, true: ...
# .y == null and .z == true
# y == null and z == true
}</syntaxhighlight>
}</syntaxhighlight>


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===implicit fallthrough===
===implicit fallthrough===
If a block of a switch has any statements, there is no implicit fallthrough. A case with an empty block after it creates an implicit fallthrough.
If a block of a switch has any statements, there is no implicit fallthrough. A case with an empty block after it creates an implicit fallthrough.
<syntaxhighlight lang="langur">switch .x {
<syntaxhighlight lang="langur">switch x {
case true:
case true:
# implicit fallthrough
# implicit fallthrough
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A fallthrough statement is allowed anywhere within a switch block, not just at the end. (It's typical in programming languages to only allow fallthrough at the end of the block.)
A fallthrough statement is allowed anywhere within a switch block, not just at the end. (It's typical in programming languages to only allow fallthrough at the end of the block.)


<syntaxhighlight lang="langur">switch .x {
<syntaxhighlight lang="langur">switch x {
case true:
case true:
if .y > 100 {
if y > 100 {
fallthrough
fallthrough
} else {
} else {
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===shortened form switch===
===shortened form switch===
A shortened form expects a single action expression per test and is more limited in other ways, as well (no explicit fallthrough, no alternate test expressions, no alternate logical operators). A default section is optional (null by default).
A shortened form expects a single action expression per test and is more limited in other ways, as well (no explicit fallthrough, no alternate test expressions, no alternate logical operators). A default section is optional (null by default).
<syntaxhighlight lang="langur">switch(.x, .y, .z;
<syntaxhighlight lang="langur">switch(x, y, z;
true: ... ; # any are equal to true
true: ... ; # any are equal to true
_, >= .z: ...; # .y >= .z
_, >= z: ...; # y >= z
... ) # default</syntaxhighlight>
... ) # default</syntaxhighlight>


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