Expressions

Additionally to simple strings, you can use expressions to set the value of an attribute. Expressions must be enclosed inside "(" and ")".

Inside expressions, you can refer to attributes simple by their name. String constants must be enclosed inside quotes.

    <$let name:string="hugo.gif">
    <IMG SRC=(name) ALT="name">

    <IMG SRC="hugo.gif" ALT="name">

Operators

• attr stands for an attribute
• expr stands for an expression

Unary operators

NOT expr

negotiate (boolean) expression

SET attr

True, if attribute has been set during macro call

DEFINDED attr

True, if attribute was defined with <$macro> or <$let>

GETENV environment variable

get value of an environment variable

Binary operators

expr = expr

string comparison (case insensitive)

expr + expr

string concatenation

    <$let name:string="hugo">
    <$let here:string="here">

    <IMG SRC=(name+".gif") ALT=(name+" was "+here)>
    <$if (name="hugo")>
    This is hugo!
    <$else>
    Maybe it's sepp?
    </$if>
    AmigaOS version: <$insert text=(GetEnv "KickStart")>

    <IMG SRC="hugo.gif" ALT="hugo was here">
    AmigaOS version: 40.63

Priorities

Important: Different to most programming languages, hsc does not support priorities for different operators. Therefor, expressions are simply processed sequentialy

But you can use nested brackets within complex expressions.

Boolean expressions

If you pass an expression to a boolean attribute, the expression is evaluated as before. If the expression returned an empty string, the boolean attribute is set to FALSE. This means, that it is removed from the tag/macro-call.

Any none-empty string enables the attribute.

    <IMG SRC=(name) ALT="nufin" ISMAP=(name="map.gif")>

    <IMG SRC="hugo.gif" ALT="nufin">

    <IMG SRC="map.gif" ALT="nufin" ISMAP>

if name has been set to "map.gif". Note that only the second call enables the boolean attribute ISMAP, while it gets stripped for the first call.