If true

Purpose: Comparison statement.

if-true <comparison>
    <any code>
[
else-if <comparison>
    <any code>
] ...
[
else-if
    <any code>
]
end-if

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if-true statement will evaluate a <comparison> and if true, it will execute <any code> that immediately follows; if false, it will evaluate the optional following <comparison> in else-if statement, and if true it will execute <any code> that immediately follows it; and so on; if none of the comparisons are true, then an optional <any code> following else-if statement will execute; regardless of which <any code> executes (or if any does), the execution will continue after end-if.

There can be only one "else-if" statement without a condition, and it must be the last one.

<comparison> is

For strings:
```
<string> \
   ( equal | not-equal | \
   lesser-than | lesser-equal | \
   greater-than | greater-equal | \
   contain | not-contain ) \
<check string> \
 [ case-insensitive ] [ length <length> ]
```
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If "equal", "not-equal", "lesser-than", "lesser-equal", "greater-than" or "greater-equal" clause is used, a comparison succeeds if <string> is equal, not equal, lesser, lesser or equal, greater or greater-or-equal than <check string>, respectively.

If "contain" or "not-contain" clause is used, a comparison succeeds if <string> is contained or not contained in <check string>, respectively.

If "case-insensitive" clause is used, a comparison is performed without case sensitivity; this option is meant for null-terminated strings, while for non-null terminated strings it produces an undefined result.

If "length" clause is used, only the first <length> bytes of the strings are compared; this clause is not available for "contain" and "not-contain".
For numbers and doubles (<value> is a number of a double):
```
<value> \
   ( equal | not-equal | \
   lesser-than | lesser-equal | \
   greater-than | greater-equal | \
   every | not-every ) \
<check value>  [ error-margin <error margin> ] ...
```
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If "equal", "not-equal", "lesser-than", "lesser-equal", "greater-than" or "greater-equal" clause is used, a comparison succeeds if <value> is equal, not equal, lesser, lesser or equal, greater or greater-or-equal than <check value>, respectively.

If "every" is used, then the comparison succeeds if the modulo of <value> and <check value> is 0 - this is useful in executing some code every N times but not the ones in between; with "not-every" the comparison success is this modulo is not 0 which is useful to execute code all the times except every Nth.

"error-margin" is valid for "equal" or "not-equal" comparisions, and for double only. Since doubles may be difficult to compare for equality, you can specify the margin of error (i.e. 1E-7), so that comparisions succeed if the difference between two doubles is lesser than this value. For instance, to limit double comparison to two decimals, "error-margin" should be 1e-2. Unless you have a reason not to use "error-margin" when comparing doubles (such as if they are rounded, or if you know how they are calculated and thus what the internal representation would be), you should always use it.

For booleans:

<boolean> ( equal | not-equal ) <check boolean>  ...

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If "equal" or "not-equal" clause is used, a comparison succeeds if <boolean> is equal or not equal than <check boolean>, respectively.

Multiple comparisons

For convenience, multiple <comparisons> can be connected by either "and" or "or" clause, but not both in the same <condition> (in order to keep comparisons readable; see boolean-expressions for constructing more involved boolean expressions). "and" clause uses logical AND to connect <comparisons> and it succeeds if all <comparison>s succeed. "or" clause uses logical OR to connect <comparisons> and it succeeds if at least one <comparison>s succeeds (if such a <comparison> is found, the following ones are not checked).

Nesting

if-true can be nested, which can be up to 30 levels deep.

Examples

%% /if-test public
    get-param inp
    if-true inp equal "1"
        @Found "1" in input
    else-if inp equal "2"  or inp equal "3"
        @Found "2" or "3" in input
        get-param inp_num
        string-number inp_num to num
        if-true num equal 4
            @Found 4 in more input
        else-if num equal 5  and  inp equal "4"
            @Found 5 in more input and "4" in input
        else-if
            @Something else
        end-if
    else-if
        @Found something else
    end-if
%%

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<string>, <number> and <boolean> can be expressions, for instance:

set-string str1="one"
set-string str2="two"
if-true str1+" "+str2 not-equal "one two"
    @It can't be true!
end-if
...
set-bool b1 = str1 not-equal "one"
set-bool b2 = str2 equal "two"
if-true b1 && b2 equal false
    @It is true!
end-if
...
set-number n1 = 20
if-true n1+10 equal 30 and !b1 equal true and str1 equal "one"
    @It is true!
end-if

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Check two doubles for equality with a margin of error - in this case they are considered equal as the margin of error is greater than the difference:

set-double d = 62009.755529200672754
if-true dl equal 62009.755529 error-margin 1E-4
    @The doubles are equal
end-if

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