Category

vczh edited this page Jan 30, 2014 · 7 revisions

Category is a way to limit the place of calling a specified block or sentence.

###Category on Sentences Some sentences are only make sense to call in some blocks, like break and repeat. Multiple blocks can share the same category, and a sentence is allowed to be limited to use inside multiple categories of blocks.

For example, if we want to limit that break can only be used inside repeat:

category
	start REPEAT
	closable
block repeat ...

category
	inside REPEAT
sentence break ...

A block can only have one start, but a sentence can have multiple inside. closable means that this block can be ended by end.

Because of the category configuration, the following statements are correct:

repeat
	break
end
repeat
	if true
		break
	end
end

Although if is not in category REPEAT, but repeat is. So break can be used in the if in repeat.

And this is not correct because break does not appear inside repeat or any other blocks that in caregory REPEAT:

try
	break
finally
end

inside is not allowed on blocks, it is the only allowed configuration for sentences.

###Category on Blocks and Block Chains You can specify follow on blocks the build a block chain!

For example, you can use block to build the if statement:

block (sentence body) if (condition)
	select condition
		case true
			body
	end
end

But what about else if and else?

To enable that, Tinymoe provides a feature called block chain. If you declare if, else if and else in the following way:

category
	start IFELSE if
	closable
block (sentence body) if (condition)
...

category (signal)
	follow IFELSE if
	start IFELSE if
	closable
block (sentence body) else if (expression condition)
...

category (signal)
	follow IFELSE if
	closable
block (sentence body) else
...

Then else if and else can be used right after if and else if because of the follow configuration. else if and else cannot be used after else also because of the follow configuration. if, else if and else can be the last block in a block chain because of the closable configuration.

The follow configuration requires that a block should be appear right after other blocks in the specified category. Multiple follow are allowed on a block.

If a block has a follow configuration, than category (signal) is required because a block should receive the return value from the previous block. For example:

if condition one
	A
else if condition two
	B
else if condition three
	C
else
	D
end

All four blocks, if, two else if and else, are executed sequencially. When condition one success, if should pass the imformation to the next else if to tell it to skip, and else if will tell the second else if to skip, and it will tell the last else to skip.

A block can pass information to the next block by writing the the result variable. A block can receive information from the previous block by the signal variable specified in category (signal).

If one of the previous blocks succeed, then the current else if should not evaluate both the condition and the body. This is why else if uses (expression condition) (see Phrases, Sentences and Blocks).

More explanation for if block series can be found in Standard Library: If Else.

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