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Units

All @_Size instances can have optional property units.

See the examples in using units cases.

Core units

There is a list of units (core units) that is included as default in Heta language. This list is based on base units in SBML specifications. The list is the following:
mole, litre, second, kilogram, katal,
item, joule, metre, dimensionless, watt,
volt, ampere, newton, becquerel, candela,
coulomb, farad, gram, gray, henry,
hertz, kelvin, lumen, lux, ohm,
pascal, radian, siemens, sievert, steradian,
tesla, weber, year, day, hour,
minute

UnitsExpr

The complex units, i.e. units which can be expresses from combination of the pre-defined units like mole/litre, m^2, etc can be expressed in form of UnitsExpr (units expression) string format.

There is some options to use dimensionless units:

  • direct use of dimensionless base unit;
  • create an synonym of it as declared in qsp-units.heta from heta-compiler;
  • use 1 value instead of dimensionless.

Example 1:

s1 @Species { units: mole/litre };

Example 2:

k1 @Const { units: mole^2/litre^2/second };

Example 3:

k1 @Const { units: 1/second };

Example 4:

x1 @Const { units: 1 }; // dimensionless

UnitsExpr with multipliers

The multiplier of units is an optional feature but if you use you must cover the component with round brackets.

Example:

s2 @Species { units: (1e-9 mole)/litre } .= 10;

UnitsComponent Array

An alternative way to set complex units is to express it in format of UnitsComponent[]. Using multiplier property one can add multiplier to the base unit.

Example:

s3 @Species {
    units: [
        { kind: mole, multiplier: 1e-9 },
        { kind: litre, exponent: -1 }
    ]
};

User defined units

User can create his own list of units and use it instead of core units. It can be done creating #defineUnit action. The units property here can be expressed by UnitsExpr or UnitsComponent[]

Example:

pM #defineUnit {
    units: [
        { kind: mole, multiplier: 1e-12 },
        { kind: litre, multiplier: 1, exponent: -1 }
    ]
};

s1 @Species { units: pM };

Units checking in compilation

Depending on a compiler the units may be checked for consistency.

See more information in Compilation chapter.