create case(variable, expression_list) function

[EduardoRSeifert]

This PR creates the case function.
It receives a variable as the first parameter, then a list of comparisons and results as the other parameters

Syntax

The list should be in this syntax:

case("variable", "comparison1;result1", "comparison2;result2", "default;default value")

Using the @ token

Variable will be treated as a string, but can be considered a number when doing an operation in the comparison. example:

case("5", "5;results in simple string") // will test if the string "5" equals "5"
case("5", "@ < 6;results in simple string") // will test if the number 5 is smaller than 6

To use the variable in a comparison operation, we use the @ token. It is also used in the result to evaluate the result instead of returning a string

case("5", "@ < 6;@5*5") // will test if the number 5 is smaller than 6 and return 25
case("string variable", "string variable;@5*5") // will match strings and return 25

Default value

It is NOT strictly needed, but should be excluded carefully. Good example of removing it:
case("5", "@<4;do this", "@>=4;do that") since the combination of the comparisons is a Tautology
case("5", "@<5;do this", "@>5;do that") herein lies the problem: 5 is neither < 5 nor > 5. Make sure there is a Tautology in the comparisons if the default value is not added (the parser will throw an error if no comparisons are satisfied and there isn't a default)
case("5", "@<5;do this", "@>5;do that", "default;something wrong happened") is the safest way to construct the case

Tests

[Victorcorcos]

Hmmm, the @ operator is having two distinct responsibilities while being the same operator, right?

1. @ < 6 → A replacement of the main value used as comparison in the case statement + Casting it to integer (at the same time).
2. @5*5 → Casting the right value to integer.

Maybe if we break it into single responsibilities it would be easier to comprehend.

For example
@ → Casting the right value to integer.
$ → Replace of the main value used as comparison in the case statement

1. @$ < 6
2. @5*5

Even simpler approach

We can use the number() function that we already have to cast the result to a number

number(case("5", "@ < 6;5*5"))

[EduardoRSeifert]

Hmmm, the @ operator is having two distinct responsibilities while being the same operator, right?

1. @ < 6 → A replacement of the main value used as comparison in the case statement + Casting it to integer (at the same time).
2. @5*5 → Casting the right value to integer.

Maybe if we break it into single responsibilities it would be easier to comprehend.

For example @ → Casting the right value to integer. $ → Replace of the main value used as comparison in the case statement

1. @$ < 6
2. @5*5

Even simpler approach

We can use the number() function that we already have to cast the result to a number

number(case("5", "@ < 6;5*5"))

You misunderstood. @ means 2 different things, yes, but it always means the same thing within it's argument. I used the same token to avoid creating a new one

@ in the comparison means "substitute @ for the variable and evaluate the resulting equation", while @ in the return value means "evaluate the return value as an equation". So case("blabla.blabla", "@ > 5;@10", "default;@8") will result in "blabla.blabla > 5 ? 10 : 8". But don't mistake @10 as cating to integer, it means "evaluate 10 as an equation", but ot RESULTS in the same as casting to integer. Hope that made it clearer. Yes, you could use case("blabla.blabla", "@ > 5;@Number(10)", "default;@Number(8)") to be more explicit that you want a number return, but is that necessary?

[Victorcorcos]

@EduardoRSeifert Got it!

---

case("5", "@ < 6;@5*5", "default;@666")

Means

case 5
when < 6
  5 * 5
else
  666
end

---

case("edimar", "xablau;nao", "edimar;sim")

Means

case "edimar"
when "xablau"
  "nao"
when "edimar"
  "sim"
end

[Victorcorcos]

There are conflicts in tests.sh now 👍

[Victorcorcos]

Very interesting and useful function!

I'm just waiting for @niltonvasques approval here.