[erlang-questions] Guards syntax for multiple values

Lars-Åke Fredlund lfredlund@REDACTED
Thu Mar 28 10:00:55 CET 2019

A good analysis.

Please consider generalising the if statements (and/or finally introduce 
a cond expression) to permit arbitrary functions; the separation between 
guard functions and normal "predicate" functions has always felt very 
artificial to me when writing code. There is a reason as Mikael says to 
keep it for the receive, but in other contexts... It just hurts 


On 27/3/19 9:57, Mikael Pettersson wrote:
> Instead of focusing on syntax, people should focus on semantics.
> The basic problem is the very presence of so-called "guard
> expressions", as a highly restricted subset of the general set of
> expressions.  The guard expression restriction is only needed in
> receives, to ensure that the mailbox doesn't change as a side-effect
> of evaluating the pattern match + guard combination.  In other
> contexts, guards could be fully general boolean expressions -- only
> historical reasons prevent them from being so.
> Personally I tend to write code to dispatch on the result of
> classification functions instead of relying on complex guards.
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