Expression syntax

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How to configure

Expressions can be configured in two ways.

Advised syntax

The advised syntax (since version 7.105) is to configure an expression after the combination of a colon and an equals sign (:=). Expressions are not quoted in this syntax.

See the following examples:

attribute <NrHa>     ForestAndNature (rdc_100l) := LandUseClass/Forest + LandUseClass/Nature;
unit<float32>           meter                                    := baseunit('m', float32);
parameter<string>  capitol                                   := 'Amsterdam';
parameter<meter> marathon                               := 42195[meter];

Original syntax

The original syntax (and only syntax until GeoDMS Version 7.104) is to configure an expression with the "expr" property. With this syntax Expressions are always configured between double quotes ("").

See the following examples:

attribute <NrHa>    ForestAndNature (rdc_100l) :  expr = "LandUseClass/Forest + LandUseClass/Nature";
unit<float32>          m:                                            expr = "baseunit('m', float32)";
parameter<string> capitol:                                     expr = "'Amsterdam'";
parameter<meter> marathon:                                expr = "42195[meter]";

This syntax is still valid, but the new syntax is advised since GeoDMS Version 7.105 as:

  1. It is shorter.
  2. It is better understood by grammar configuration files for example in Crimson Editor.
  3. Double quotes in strings can be used without indirections.

Components

Expressions consist of one or a combination of the following components:

  1. other data items, see example 1
  2. operators and functions, see example 1,2,4
  3. constants, see example 3 and 4
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