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F# "this rule will never be matched" expression in a NOT recursive function


F# "this rule will never be matched" expression in a NOT recursive function

By : user2950202
Date : November 17 2020, 11:52 AM
I hope this helps you . You can't match against a variable, I mean you can but if you do so what would happen is that the variable will be bound to that value and it seems to me that's not what you are trying to do, otherwise the first case in your code will "eat" all other cases and that's why the following rules will never be matched.
You can either match with a condition:
code :
let RotateFace (face: int, turns: int) =
    match face with
        | x when x = upperface -> 
            TiltCube(2)
            TwistCube(turns)
            TiltCube(2)
[<Literal>]
let Upperface  = 4

let RotateFace (face: int, turns: int) =
    match face with
        | Upperface -> 
            TiltCube(2)
            TwistCube(turns)
            TiltCube(2)


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Bison build warning: "-s option given but default rule can be matched"

Bison build warning: "-s option given but default rule can be matched"


By : Theo Sang Yub Kim
Date : March 29 2020, 07:55 AM
Does that help I get the warning , %option nodefault is equivalent to -s
Setting up rules for Flex, warning:"rule cannot be matched"

Setting up rules for Flex, warning:"rule cannot be matched"


By : Fabio Manfredini
Date : March 29 2020, 07:55 AM
Hope this helps I believe the issue here is that flex uses spaces to delimit tokens for regex matching. So when it parses your file it is treating everything after "^User-Agent:" as part of the action. You can make this work by escaping the space:
code :
^User-Agent:\ [^\n]*Firefox
^User-Agent:\ [^\n]*MSIE
^User-Agent:\ [^\n]*Opera
^User-Agent:\ [^\n]*Safari
F# Partial Active Pattern Matching "Rule Will Never Be Matched"

F# Partial Active Pattern Matching "Rule Will Never Be Matched"


By : Priti
Date : March 29 2020, 07:55 AM
I wish this help you I think you should add the None case to the active pattern declaration as follows:
code :
let (| HasMatch | _ |) (x:string) = 
  if x.Contains("0") then Some()
  else None;;
f# match expression - "rule will never be matched"

f# match expression - "rule will never be matched"


By : Serj Gavrilyuk
Date : March 29 2020, 07:55 AM
hope this fix your issue I'm trying to learn F# and I've come to a point where I don't understand what I am doing wrong. I wrote the following code: , I think you want:
code :
let rec sense world probs measurement = 
    match world, probs with
    | m::row, p::rop when m = measurement -> (p*pHit)::sense row rop measurement
    | _::row, p::rop -> (p*pMiss)::sense row rop measurement
    | [],_ -> []
    | _,[] -> []
"warning, rule cannot be matched" Defining String in lex

"warning, rule cannot be matched" Defining String in lex


By : Jatin
Date : March 29 2020, 07:55 AM
wish help you to fix your issue When there are multiple rules that can match on the current input and produce a match of the same size, flex will take the rule that's defined first.
So, for example, if there's a \t, both the rules \t and . could match, but \t comes first, so it's the one that's used. But if a " appears, . is used because \" comes after it in your flex file. So there's no way that the \" rule in STRLIT would ever be used and that's what the error is about.
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