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conditional indention
f#

According the F# spec, then, elif and else are allowed to lineup with the if keyword as in: 

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if a = 1 then "one" 
elif a = 2 
then "two" 
else "> two"

And I can indent the body of each conditional: 

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if a = 1 then 
    "one" 
elif a = 2 
then 
    "two" 
else 
    "> two"



However, I can undent the body of the else statement without a syntax warning: 

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if a = 1 then 
"one" // possible incorrect indentation: this token is offside of context started at position (2:1). Try indenting this token further or using standard formatting conventions 
elif a = 2 
then 
"two" // possible incorrect indentation: this token is offside of context started at position (5:1). Try indenting this token further or using standard formatting conventions 
else 
"> two" // ok?

Am I misreading the language spec? Is this a bug in the lexical filter or is this intended to be valid #light syntax?

.

Hi there,

This is intentional. One of the issues with an expression-based language is that it is difficult to specify "early return" values in checking cut-out code at the start of a function. This syntax lets you do this without requiring further indentation for each case, e.g. consider this (fairly nonsensical... ) code:

let f x y =

if x < 0 then 0 else

let diff = y - x

if diff > 100 || y > 100 then 100 else

diff * 2

Here the "bodies of the "else" do align with the "if".

Kind regards

don

By on 4/23/2009 3:11 PM ()

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