feat: adds else if and else conditional clauses
#699
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claymcleod
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I agree with this, though I'll admit my programming background bias. I find it more complicated to create two unconnected @geoffjentry said:
And I can point to at least one instance of this pattern in our |
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| ### Conditional Statement | |||
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| A conditional statement consists of the `if` keyword, followed by a `Boolean` expression and a body of (potentially nested) statements. The conditional body is only evaluated if the conditional expression evaluates to `true`. | |||
| A conditional statement consists of one or more conditional clauses. Each conditional clause is comprised of an expression that evaluates to a `Boolean` and an associated clause body. When a conditional statement is executed, each of the conditional clauses is evaluated sequentially: (a) the expression for that clause is evaluated and, if the returned value is `true`, the body of that clause is executed and the entire conditional statement suspends further execution. The simplest conditional statement contains a single "if" clause, which is the `if` keyword, followed by the clause's boolean expression, and, finally, the clause body of (potentially nested) statements wrapped in curly brackets. | |||
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| After evaluation of the conditional has completed, each declaration or call output in the conditional body is exposed in the enclosing context as an optional declaration. In other words, for a declaration or call output `T <name>` within a conditional body, a declaration `T? <name>` is implicitly available outside of the conditional body. If the expression evaluated to `true`, and thus the body of the conditional was evaluated, then the value of each exposed declaration is the same as its original value inside the conditional body. If the expression evaluated to `false` and thus the body of the conditional was not evaluated, then the value of each exposed declaration is `None`. | |||
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I feel like this paragraph probably needs to be expanded upon.
It should probably read that the declarations within the if, else if, or else body that executes (depending on the evaluation of the conditional expressions) will be assigned to the values of their declarations; the declarations in the bodies that did not execute will be None.
This change proposes extending conditional statements to include
else ifandelseclauses.These types of clauses have been proposed many times on Slack and more formally in #268 and #697. Overall, the feedback seems positive, though concerns have been raised as to whether the cost of added complexity is worth it (see #697 for more details). I have made my case at the end of #697 that I feel it's actually removing mental burden/complexity to add these clauses into the language.
Closes #268.
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README.mdor other documentation to account for these changes (when appropriate).CHANGELOG.mddescribing the change and linking back to your pull request.CONTRIBUTING.mddocument.