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H.2  Passing Simple Parameters to Routines

Understanding SheerPower Routine Parameters

SheerPower routines can handle up to 32 parameters in total, divided into two categories:

  • Up to 16 parameters can be passed into routines.
  • Up to 16 parameters can be returned from routines.
The with clause contains the names of the parameters coming into the routine. The returning clause contains the names of the parameters returned by the routine.

Parameter Passing

Parameters Passed into a Routine:

These are passed by value, meaning their values cannot be altered by the routine, with the exception of clusters.

Clusters are passed by reference, allowing the routine to modify the cluster, such as adding new rows to a cluster array or changing cluster field values.

Strings Passed into a Routine:

Optimized for performance, so passing the same string multiple times incurs virtually no performance penalty.

Returning Parameters:

New values are assigned by copying data into them.

Returning the same string multiple times is also optimized for performance, resulting in minimal impact.

Advantages of Named Parameters in SheerPower Routines

  • Clarity: Named parameters enhance code readability by clearly indicating the purpose of each parameter.
  • Order Independence: Parameters can be specified in any order, providing flexibility in coding.
  • Self-documenting Code: Named parameters serve as inline documentation, reducing the need for extensive comments.
  • Maintainability: Explicitly named parameters make it easier to manage changes to parameter lists.
  • Error Reduction: The risk of mixing up parameters is minimized, reducing potential bugs.

Tip: For easier and clearer coding, name your variables the same as the routine's parameters. This allows you to call a routine using just the variable names, in any order, and SheerPower will automatically match them to the corresponding parameters.



Example of Named Parameter Usage

routine calculate_tax with income, tax_rate, returning tax_amount tax_amount = income * tax_rate end routine calculate_tax with income=50_000, tax_rate=0.2, returning tax_amount result print "Tax Amount: "; result // using implied parameter values income = 50_000 tax_rate = 0.2 calculate_tax with income, tax_rate, returning tax_amount print "Tax Amount: "; tax_amount

Routines can also be called without any parameters at all. This is typical for global routines. Private and scoped routines tend to always have parameters.
Here is an example of a private routine that calculates tax. We will pass into it an amount and a tax rate. It will return the tax due.
profit = 1234 tax_rate = 6.5/100 calculate_tax_due with amount profit, rate tax_rate, returning due tax_due print 'Tax due: '; tax_due private routine calculate_tax_due with amount, rate, returning due due = amount * rate end routine
The with clause contains the names of the parameters coming into the routine. The returning clause contains the names of the parameters returned by the routine.

There can be up to 16 parameters in the with clause and up to another 16 parameters in the returning clause. From a maintenance standpoint, it is recommended to keep the number of parameters to just a few. If you need to pass in or out a lot of data, use cluster parameters (see next tutorial).


Simplified routine parameters
When passing parameters to routines, often there is a pattern of coding:
myamount = 45 myrate = 5.6 calculate_tax_due with amount=myamount, tax_rate=myrate, returning due mydue private routine calculate_tax_due with amount, tax_rate, returning due due = amount * tax_rate end routine
Instead, we could use this code, taking advantage of optional "=".:
amount = 45 tax_rate = 5.6 calculate_tax_due with amount amount, tax_rate tax_rate, returning due due
and even further simplify it, taking advantage of implied parameters:
amount = 45 tax_rate = 5.6 calculate_tax_due with amount, tax_rate, returning due
These examples all produce equivalent results where the last example is the simplest.
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